Add mypy and bump minimum supported python version to 3.9

The agreed minimum supported python version is the one that is in the current stable Debian distribution.
Using Python 3.9 allows us to make use of the new typing annotations.

Signed-off-by: Ivan Kanakarakis <ivan.kanak@gmail.com>

2 files changed, 56 insertions, 228 deletions

diff --git a/poetry.lock b/poetry.lock
index e70158eb..b9356059 100644
--- a/poetry.lock
+++ b/poetry.lock
@@ -116,12 +116,10 @@ files = [
 
 [package.dependencies]
 click = ">=8.0.0"
-dataclasses = {version = ">=0.6", markers = "python_version < \"3.7\""}
 mypy-extensions = ">=0.4.3"
 pathspec = ">=0.9.0"
 platformdirs = ">=2"
 tomli = {version = ">=1.1.0", markers = "python_full_version < \"3.11.0a7\""}
-typed-ast = {version = ">=1.4.2", markers = "python_version < \"3.8\" and implementation_name == \"cpython\""}
 typing-extensions = {version = ">=3.10.0.0", markers = "python_version < \"3.10\""}
 
 [package.extras]
@@ -248,7 +246,6 @@ files = [
 
 [package.dependencies]
 colorama = {version = "*", markers = "platform_system == \"Windows\""}
-importlib-metadata = {version = "*", markers = "python_version < \"3.8\""}
 
 [[package]]
 name = "colorama"
@@ -372,18 +369,6 @@ test-randomorder = ["pytest-randomly"]
 tox = ["tox"]
 
 [[package]]
-name = "dataclasses"
-version = "0.8"
-description = "A backport of the dataclasses module for Python 3.6"
-category = "dev"
-optional = false
-python-versions = ">=3.6, <3.7"
-files = [
-    {file = "dataclasses-0.8-py3-none-any.whl", hash = "sha256:0201d89fa866f68c8ebd9d08ee6ff50c0b255f8ec63a71c16fda7af82bb887bf"},
-    {file = "dataclasses-0.8.tar.gz", hash = "sha256:8479067f342acf957dc82ec415d355ab5edb7e7646b90dc6e2fd1d96ad084c97"},
-]
-
-[[package]]
 name = "decorator"
 version = "5.1.1"
 description = "Decorators for Humans"
@@ -475,7 +460,6 @@ files = [
 ]
 
 [package.dependencies]
-importlib-metadata = {version = ">=1.1.0,<4.3", markers = "python_version < \"3.8\""}
 mccabe = ">=0.7.0,<0.8.0"
 pycodestyle = ">=2.9.0,<2.10.0"
 pyflakes = ">=2.5.0,<2.6.0"
@@ -527,10 +511,7 @@ files = [
 
 [package.dependencies]
 Flake8 = ">=5"
-TOMLi = [
-    {version = "*", markers = "python_version < \"3.11\""},
-    {version = "<2", markers = "python_version < \"3.7\""},
-]
+TOMLi = {version = "*", markers = "python_version < \"3.11\""}
 
 [package.extras]
 dev = ["pyTest", "pyTest-cov"]
@@ -560,45 +541,6 @@ files = [
 ]
 
 [[package]]
-name = "importlib-metadata"
-version = "4.2.0"
-description = "Read metadata from Python packages"
-category = "main"
-optional = false
-python-versions = ">=3.6"
-files = [
-    {file = "importlib_metadata-4.2.0-py3-none-any.whl", hash = "sha256:057e92c15bc8d9e8109738a48db0ccb31b4d9d5cfbee5a8670879a30be66304b"},
-    {file = "importlib_metadata-4.2.0.tar.gz", hash = "sha256:b7e52a1f8dec14a75ea73e0891f3060099ca1d8e6a462a4dff11c3e119ea1b31"},
-]
-
-[package.dependencies]
-typing-extensions = {version = ">=3.6.4", markers = "python_version < \"3.8\""}
-zipp = ">=0.5"
-
-[package.extras]
-docs = ["jaraco.packaging (>=8.2)", "rst.linker (>=1.9)", "sphinx"]
-testing = ["flufl.flake8", "importlib-resources (>=1.3)", "packaging", "pep517", "pyfakefs", "pytest (>=4.6)", "pytest-black (>=0.3.7)", "pytest-checkdocs (>=2.4)", "pytest-cov", "pytest-enabler (>=1.0.1)", "pytest-flake8", "pytest-mypy"]
-
-[[package]]
-name = "importlib-resources"
-version = "5.4.0"
-description = "Read resources from Python packages"
-category = "main"
-optional = false
-python-versions = ">=3.6"
-files = [
-    {file = "importlib_resources-5.4.0-py3-none-any.whl", hash = "sha256:33a95faed5fc19b4bc16b29a6eeae248a3fe69dd55d4d229d2b480e23eeaad45"},
-    {file = "importlib_resources-5.4.0.tar.gz", hash = "sha256:d756e2f85dd4de2ba89be0b21dba2a3bbec2e871a42a3a16719258a11f87506b"},
-]
-
-[package.dependencies]
-zipp = {version = ">=3.1.0", markers = "python_version < \"3.10\""}
-
-[package.extras]
-docs = ["jaraco.packaging (>=8.2)", "rst.linker (>=1.9)", "sphinx"]
-testing = ["pytest (>=6)", "pytest-black (>=0.3.7)", "pytest-checkdocs (>=2.4)", "pytest-cov", "pytest-enabler (>=1.0.1)", "pytest-flake8", "pytest-mypy"]
-
-[[package]]
 name = "iniconfig"
 version = "1.1.1"
 description = "iniconfig: brain-dead simple config-ini parsing"
@@ -623,48 +565,9 @@ files = [
 ]
 
 [package.dependencies]
-decorator = {version = "*", markers = "python_version >= \"3.6\""}
-ipython = [
-    {version = ">=7.16.3,<7.17.0", markers = "python_version == \"3.6\""},
-    {version = ">=7.31.1", markers = "python_version > \"3.6\""},
-]
-tomli = {version = "*", markers = "python_version >= \"3.6\" and python_version < \"3.11\""}
-
-[[package]]
-name = "ipython"
-version = "7.16.3"
-description = "IPython: Productive Interactive Computing"
-category = "dev"
-optional = false
-python-versions = ">=3.6"
-files = [
-    {file = "ipython-7.16.3-py3-none-any.whl", hash = "sha256:c0427ed8bc33ac481faf9d3acf7e84e0010cdaada945e0badd1e2e74cc075833"},
-    {file = "ipython-7.16.3.tar.gz", hash = "sha256:5ac47dc9af66fc2f5530c12069390877ae372ac905edca75a92a6e363b5d7caa"},
-]
-
-[package.dependencies]
-appnope = {version = "*", markers = "sys_platform == \"darwin\""}
-backcall = "*"
-colorama = {version = "*", markers = "sys_platform == \"win32\""}
-decorator = "*"
-jedi = ">=0.10,<=0.17.2"
-pexpect = {version = "*", markers = "sys_platform != \"win32\""}
-pickleshare = "*"
-prompt-toolkit = ">=2.0.0,<3.0.0 || >3.0.0,<3.0.1 || >3.0.1,<3.1.0"
-pygments = "*"
-setuptools = ">=18.5"
-traitlets = ">=4.2"
-
-[package.extras]
-all = ["Sphinx (>=1.3)", "ipykernel", "ipyparallel", "ipywidgets", "nbconvert", "nbformat", "nose (>=0.10.1)", "notebook", "numpy (>=1.14)", "pygments", "qtconsole", "requests", "testpath"]
-doc = ["Sphinx (>=1.3)"]
-kernel = ["ipykernel"]
-nbconvert = ["nbconvert"]
-nbformat = ["nbformat"]
-notebook = ["ipywidgets", "notebook"]
-parallel = ["ipyparallel"]
-qtconsole = ["qtconsole"]
-test = ["ipykernel", "nbformat", "nose (>=0.10.1)", "numpy (>=1.14)", "pygments", "requests", "testpath"]
+decorator = {version = "*", markers = "python_version > \"3.6\""}
+ipython = {version = ">=7.31.1", markers = "python_version > \"3.6\""}
+tomli = {version = "*", markers = "python_version > \"3.6\" and python_version < \"3.11\""}
 
 [[package]]
 name = "ipython"
@@ -704,18 +607,6 @@ qtconsole = ["qtconsole"]
 test = ["ipykernel", "nbformat", "nose (>=0.10.1)", "numpy (>=1.17)", "pygments", "requests", "testpath"]
 
 [[package]]
-name = "ipython-genutils"
-version = "0.2.0"
-description = "Vestigial utilities from IPython"
-category = "dev"
-optional = false
-python-versions = "*"
-files = [
-    {file = "ipython_genutils-0.2.0-py2.py3-none-any.whl", hash = "sha256:72dd37233799e619666c9f639a9da83c34013a73e8bbc79a7a6348d93c61fab8"},
-    {file = "ipython_genutils-0.2.0.tar.gz", hash = "sha256:eb2e116e75ecef9d4d228fdc66af54269afa26ab4463042e33785b887c628ba8"},
-]
-
-[[package]]
 name = "isort"
 version = "5.10.1"
 description = "A Python utility / library to sort Python imports."
@@ -735,25 +626,6 @@ requirements-deprecated-finder = ["pip-api", "pipreqs"]
 
 [[package]]
 name = "jedi"
-version = "0.17.2"
-description = "An autocompletion tool for Python that can be used for text editors."
-category = "dev"
-optional = false
-python-versions = ">=2.7, !=3.0.*, !=3.1.*, !=3.2.*, !=3.3.*, !=3.4.*"
-files = [
-    {file = "jedi-0.17.2-py2.py3-none-any.whl", hash = "sha256:98cc583fa0f2f8304968199b01b6b4b94f469a1f4a74c1560506ca2a211378b5"},
-    {file = "jedi-0.17.2.tar.gz", hash = "sha256:86ed7d9b750603e4ba582ea8edc678657fb4007894a12bcf6f4bb97892f31d20"},
-]
-
-[package.dependencies]
-parso = ">=0.7.0,<0.8.0"
-
-[package.extras]
-qa = ["flake8 (==3.7.9)"]
-testing = ["Django (<3.1)", "colorama", "docopt", "pytest (>=3.9.0,<5.0.0)"]
-
-[[package]]
-name = "jedi"
 version = "0.18.2"
 description = "An autocompletion tool for Python that can be used for text editors."
 category = "dev"
@@ -897,6 +769,53 @@ files = [
 ]
 
 [[package]]
+name = "mypy"
+version = "1.0.0"
+description = "Optional static typing for Python"
+category = "dev"
+optional = false
+python-versions = ">=3.7"
+files = [
+    {file = "mypy-1.0.0-cp310-cp310-macosx_10_9_x86_64.whl", hash = "sha256:e0626db16705ab9f7fa6c249c017c887baf20738ce7f9129da162bb3075fc1af"},
+    {file = "mypy-1.0.0-cp310-cp310-macosx_11_0_arm64.whl", hash = "sha256:1ace23f6bb4aec4604b86c4843276e8fa548d667dbbd0cb83a3ae14b18b2db6c"},
+    {file = "mypy-1.0.0-cp310-cp310-manylinux_2_17_x86_64.manylinux2014_x86_64.whl", hash = "sha256:87edfaf344c9401942883fad030909116aa77b0fa7e6e8e1c5407e14549afe9a"},
+    {file = "mypy-1.0.0-cp310-cp310-musllinux_1_1_x86_64.whl", hash = "sha256:0ab090d9240d6b4e99e1fa998c2d0aa5b29fc0fb06bd30e7ad6183c95fa07593"},
+    {file = "mypy-1.0.0-cp310-cp310-win_amd64.whl", hash = "sha256:7cc2c01dfc5a3cbddfa6c13f530ef3b95292f926329929001d45e124342cd6b7"},
+    {file = "mypy-1.0.0-cp311-cp311-macosx_10_9_x86_64.whl", hash = "sha256:14d776869a3e6c89c17eb943100f7868f677703c8a4e00b3803918f86aafbc52"},
+    {file = "mypy-1.0.0-cp311-cp311-macosx_11_0_arm64.whl", hash = "sha256:bb2782a036d9eb6b5a6efcdda0986774bf798beef86a62da86cb73e2a10b423d"},
+    {file = "mypy-1.0.0-cp311-cp311-manylinux_2_17_x86_64.manylinux2014_x86_64.whl", hash = "sha256:5cfca124f0ac6707747544c127880893ad72a656e136adc935c8600740b21ff5"},
+    {file = "mypy-1.0.0-cp311-cp311-musllinux_1_1_x86_64.whl", hash = "sha256:8845125d0b7c57838a10fd8925b0f5f709d0e08568ce587cc862aacce453e3dd"},
+    {file = "mypy-1.0.0-cp311-cp311-win_amd64.whl", hash = "sha256:01b1b9e1ed40544ef486fa8ac022232ccc57109f379611633ede8e71630d07d2"},
+    {file = "mypy-1.0.0-cp37-cp37m-macosx_10_9_x86_64.whl", hash = "sha256:c7cf862aef988b5fbaa17764ad1d21b4831436701c7d2b653156a9497d92c83c"},
+    {file = "mypy-1.0.0-cp37-cp37m-manylinux_2_17_x86_64.manylinux2014_x86_64.whl", hash = "sha256:5cd187d92b6939617f1168a4fe68f68add749902c010e66fe574c165c742ed88"},
+    {file = "mypy-1.0.0-cp37-cp37m-musllinux_1_1_x86_64.whl", hash = "sha256:4e5175026618c178dfba6188228b845b64131034ab3ba52acaffa8f6c361f805"},
+    {file = "mypy-1.0.0-cp37-cp37m-win_amd64.whl", hash = "sha256:2f6ac8c87e046dc18c7d1d7f6653a66787a4555085b056fe2d599f1f1a2a2d21"},
+    {file = "mypy-1.0.0-cp38-cp38-macosx_10_9_x86_64.whl", hash = "sha256:7306edca1c6f1b5fa0bc9aa645e6ac8393014fa82d0fa180d0ebc990ebe15964"},
+    {file = "mypy-1.0.0-cp38-cp38-macosx_11_0_arm64.whl", hash = "sha256:3cfad08f16a9c6611e6143485a93de0e1e13f48cfb90bcad7d5fde1c0cec3d36"},
+    {file = "mypy-1.0.0-cp38-cp38-manylinux_2_17_x86_64.manylinux2014_x86_64.whl", hash = "sha256:67cced7f15654710386e5c10b96608f1ee3d5c94ca1da5a2aad5889793a824c1"},
+    {file = "mypy-1.0.0-cp38-cp38-musllinux_1_1_x86_64.whl", hash = "sha256:a86b794e8a56ada65c573183756eac8ac5b8d3d59daf9d5ebd72ecdbb7867a43"},
+    {file = "mypy-1.0.0-cp38-cp38-win_amd64.whl", hash = "sha256:50979d5efff8d4135d9db293c6cb2c42260e70fb010cbc697b1311a4d7a39ddb"},
+    {file = "mypy-1.0.0-cp39-cp39-macosx_10_9_x86_64.whl", hash = "sha256:3ae4c7a99e5153496243146a3baf33b9beff714464ca386b5f62daad601d87af"},
+    {file = "mypy-1.0.0-cp39-cp39-macosx_11_0_arm64.whl", hash = "sha256:5e398652d005a198a7f3c132426b33c6b85d98aa7dc852137a2a3be8890c4072"},
+    {file = "mypy-1.0.0-cp39-cp39-manylinux_2_17_x86_64.manylinux2014_x86_64.whl", hash = "sha256:be78077064d016bc1b639c2cbcc5be945b47b4261a4f4b7d8923f6c69c5c9457"},
+    {file = "mypy-1.0.0-cp39-cp39-musllinux_1_1_x86_64.whl", hash = "sha256:92024447a339400ea00ac228369cd242e988dd775640755fa4ac0c126e49bb74"},
+    {file = "mypy-1.0.0-cp39-cp39-win_amd64.whl", hash = "sha256:fe523fcbd52c05040c7bee370d66fee8373c5972171e4fbc323153433198592d"},
+    {file = "mypy-1.0.0-py3-none-any.whl", hash = "sha256:2efa963bdddb27cb4a0d42545cd137a8d2b883bd181bbc4525b568ef6eca258f"},
+    {file = "mypy-1.0.0.tar.gz", hash = "sha256:f34495079c8d9da05b183f9f7daec2878280c2ad7cc81da686ef0b484cea2ecf"},
+]
+
+[package.dependencies]
+mypy-extensions = ">=0.4.3"
+tomli = {version = ">=1.1.0", markers = "python_version < \"3.11\""}
+typing-extensions = ">=3.10"
+
+[package.extras]
+dmypy = ["psutil (>=4.0)"]
+install-types = ["pip"]
+python2 = ["typed-ast (>=1.4.0,<2)"]
+reports = ["lxml"]
+
+[[package]]
 name = "mypy-extensions"
 version = "1.0.0"
 description = "Type system extensions for programs checked with the mypy type checker."
@@ -925,21 +844,6 @@ pyparsing = ">=2.0.2,<3.0.5 || >3.0.5"
 
 [[package]]
 name = "parso"
-version = "0.7.1"
-description = "A Python Parser"
-category = "dev"
-optional = false
-python-versions = ">=2.7, !=3.0.*, !=3.1.*, !=3.2.*, !=3.3.*"
-files = [
-    {file = "parso-0.7.1-py2.py3-none-any.whl", hash = "sha256:97218d9159b2520ff45eb78028ba8b50d2bc61dcc062a9682666f2dc4bd331ea"},
-    {file = "parso-0.7.1.tar.gz", hash = "sha256:caba44724b994a8a5e086460bb212abc5a8bc46951bf4a9a1210745953622eb9"},
-]
-
-[package.extras]
-testing = ["docopt", "pytest (>=3.0.7)"]
-
-[[package]]
-name = "parso"
 version = "0.8.3"
 description = "A Python Parser"
 category = "dev"
@@ -1041,9 +945,6 @@ files = [
     {file = "pluggy-1.0.0.tar.gz", hash = "sha256:4224373bacce55f955a878bf9cfa763c1e360858e330072059e10bad68531159"},
 ]
 
-[package.dependencies]
-importlib-metadata = {version = ">=0.12", markers = "python_version < \"3.8\""}
-
 [package.extras]
 dev = ["pre-commit", "tox"]
 testing = ["pytest", "pytest-benchmark"]
@@ -1313,7 +1214,6 @@ files = [
 atomicwrites = {version = ">=1.0", markers = "sys_platform == \"win32\""}
 attrs = ">=19.2.0"
 colorama = {version = "*", markers = "sys_platform == \"win32\""}
-importlib-metadata = {version = ">=0.12", markers = "python_version < \"3.8\""}
 iniconfig = "*"
 packaging = "*"
 pluggy = ">=0.12,<2.0"
@@ -1641,7 +1541,6 @@ files = [
 [package.dependencies]
 colorama = {version = ">=0.4.1", markers = "platform_system == \"Windows\""}
 filelock = ">=3.0.0"
-importlib-metadata = {version = ">=0.12", markers = "python_version < \"3.8\""}
 packaging = ">=14"
 pluggy = ">=0.12.0"
 py = ">=1.4.17"
@@ -1655,26 +1554,6 @@ testing = ["flaky (>=3.4.0)", "freezegun (>=0.3.11)", "pathlib2 (>=2.3.3)", "psu
 
 [[package]]
 name = "traitlets"
-version = "4.3.3"
-description = "Traitlets Python config system"
-category = "dev"
-optional = false
-python-versions = "*"
-files = [
-    {file = "traitlets-4.3.3-py2.py3-none-any.whl", hash = "sha256:70b4c6a1d9019d7b4f6846832288f86998aa3b9207c6821f3578a6a6a467fe44"},
-    {file = "traitlets-4.3.3.tar.gz", hash = "sha256:d023ee369ddd2763310e4c3eae1ff649689440d4ae59d7485eb4cfbbe3e359f7"},
-]
-
-[package.dependencies]
-decorator = "*"
-ipython-genutils = "*"
-six = "*"
-
-[package.extras]
-test = ["mock", "pytest"]
-
-[[package]]
-name = "traitlets"
 version = "5.9.0"
 description = "Traitlets Python configuration system"
 category = "dev"
@@ -1690,44 +1569,10 @@ docs = ["myst-parser", "pydata-sphinx-theme", "sphinx"]
 test = ["argcomplete (>=2.0)", "pre-commit", "pytest", "pytest-mock"]
 
 [[package]]
-name = "typed-ast"
-version = "1.5.4"
-description = "a fork of Python 2 and 3 ast modules with type comment support"
-category = "dev"
-optional = false
-python-versions = ">=3.6"
-files = [
-    {file = "typed_ast-1.5.4-cp310-cp310-macosx_10_9_x86_64.whl", hash = "sha256:669dd0c4167f6f2cd9f57041e03c3c2ebf9063d0757dc89f79ba1daa2bfca9d4"},
-    {file = "typed_ast-1.5.4-cp310-cp310-macosx_11_0_arm64.whl", hash = "sha256:211260621ab1cd7324e0798d6be953d00b74e0428382991adfddb352252f1d62"},
-    {file = "typed_ast-1.5.4-cp310-cp310-manylinux_2_17_aarch64.manylinux2014_aarch64.whl", hash = "sha256:267e3f78697a6c00c689c03db4876dd1efdfea2f251a5ad6555e82a26847b4ac"},
-    {file = "typed_ast-1.5.4-cp310-cp310-manylinux_2_5_x86_64.manylinux1_x86_64.manylinux_2_12_x86_64.manylinux2010_x86_64.whl", hash = "sha256:c542eeda69212fa10a7ada75e668876fdec5f856cd3d06829e6aa64ad17c8dfe"},
-    {file = "typed_ast-1.5.4-cp310-cp310-win_amd64.whl", hash = "sha256:a9916d2bb8865f973824fb47436fa45e1ebf2efd920f2b9f99342cb7fab93f72"},
-    {file = "typed_ast-1.5.4-cp36-cp36m-macosx_10_9_x86_64.whl", hash = "sha256:79b1e0869db7c830ba6a981d58711c88b6677506e648496b1f64ac7d15633aec"},
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-    {file = "typed_ast-1.5.4.tar.gz", hash = "sha256:39e21ceb7388e4bb37f4c679d72707ed46c2fbf2a5609b8b8ebc4b067d977df2"},
-]
-
-[[package]]
 name = "typing-extensions"
 version = "4.1.1"
 description = "Backported and Experimental Type Hints for Python 3.6+"
-category = "main"
+category = "dev"
 optional = false
 python-versions = ">=3.6"
 files = [
@@ -1767,8 +1612,6 @@ files = [
 [package.dependencies]
 distlib = ">=0.3.1,<1"
 filelock = ">=3.2,<4"
-importlib-metadata = {version = ">=0.12", markers = "python_version < \"3.8\""}
-importlib-resources = {version = ">=1.0", markers = "python_version < \"3.7\""}
 platformdirs = ">=2,<3"
 
 [package.extras]
@@ -1824,22 +1667,6 @@ dev = ["Sphinx", "coverage", "elementpath (>=2.4.0,<3.0.0)", "flake8", "jinja2",
 docs = ["Sphinx", "elementpath (>=2.4.0,<3.0.0)", "jinja2", "sphinx-rtd-theme"]
 
 [[package]]
-name = "zipp"
-version = "3.6.0"
-description = "Backport of pathlib-compatible object wrapper for zip files"
-category = "main"
-optional = false
-python-versions = ">=3.6"
-files = [
-    {file = "zipp-3.6.0-py3-none-any.whl", hash = "sha256:9fe5ea21568a0a70e50f273397638d39b03353731e6cbbb3fd8502a33fec40bc"},
-    {file = "zipp-3.6.0.tar.gz", hash = "sha256:71c644c5369f4a6e07636f0aa966270449561fcea2e3d6747b8d23efaa9d7832"},
-]
-
-[package.extras]
-docs = ["jaraco.packaging (>=8.2)", "rst.linker (>=1.9)", "sphinx"]
-testing = ["func-timeout", "jaraco.itertools", "pytest (>=4.6)", "pytest-black (>=0.3.7)", "pytest-checkdocs (>=2.4)", "pytest-cov", "pytest-enabler (>=1.0.1)", "pytest-flake8", "pytest-mypy"]
-
-[[package]]
 name = "zope-interface"
 version = "5.5.2"
 description = "Interfaces for Python"
@@ -1898,5 +1725,5 @@ s2repoze = ["paste", "repoze.who", "zope.interface"]
 
 [metadata]
 lock-version = "2.0"
-python-versions = "^3.6.2"
-content-hash = "35d49afe7b4c13990ebf30816368f5cf12c651c22ae9c882b1a922d4a7e12c0f"
+python-versions = "^3.9"
+content-hash = "2260cbaad1095829f916e07aaebe608e5e4abafdd11739e7fded09dd8112fcdc"
diff --git a/pyproject.toml b/pyproject.toml
index 6f9ec662..a2748128 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -37,7 +37,7 @@ merge_metadata = "saml2.tools.merge_metadata:main"
 parse_xsd2 = "saml2.tools.parse_xsd2:main"
 
 [tool.poetry.dependencies]
-python = "^3.6.2"
+python = "^3.9"
 cryptography = ">=3.1"
 defusedxml = "*"
 importlib-metadata = {version = ">=1.7.0", python = "<3.8"}
@@ -66,6 +66,7 @@ Flake8-pyproject = "^1.1.0.post0"
 flake8-bugbear = "^22.8.23"
 flake8-logging-format = "^0.7.5"
 ipdb = "^0.13.9"
+mypy = "^1.0.0"
 
 [tool.poetry.group.test]
 optional = true