More type hints for `rdflib.graph` and related (#1853)

This patch primarily adds more type hints for `rdflib.graph`, but also
adds type hints to some related modules in order to work with the new
type hints for `rdflib.graph`.

I'm mainly doing this as a baseline for adding type hints to
`rdflib.store`.

I have created type aliases to make it easier to type everything
consistently and to make type hints easier easier to change in the
future. The type aliases are private however (i.e. `_`-prefixed) and
should be kept as such for now.

This patch only contains typing changes and does not change runtime
behavior.

Broken off from https://github.com/RDFLib/rdflib/pull/1850

1 files changed, 8 insertions, 9 deletions

diff --git a/rdflib/util.py b/rdflib/util.py
index 328a8743..c3d04065 100644
--- a/rdflib/util.py
+++ b/rdflib/util.py
@@ -29,7 +29,7 @@ from typing import (
     TYPE_CHECKING,
     Any,
     Callable,
-    Iterable,
+    Iterator,
     List,
     Optional,
     Set,
@@ -41,7 +41,7 @@ from urllib.parse import quote, urlsplit, urlunsplit
 import rdflib.graph  # avoid circular dependency
 from rdflib.compat import sign
 from rdflib.namespace import XSD, Namespace, NamespaceManager
-from rdflib.term import BNode, IdentifiedNode, Literal, Node, URIRef
+from rdflib.term import BNode, Literal, Node, URIRef
 
 if TYPE_CHECKING:
     from rdflib.graph import Graph
@@ -409,13 +409,13 @@ def find_roots(
 
 def get_tree(
     graph: "Graph",
-    root: "IdentifiedNode",
+    root: "Node",
     prop: "URIRef",
-    mapper: Callable[["IdentifiedNode"], "IdentifiedNode"] = lambda x: x,
+    mapper: Callable[["Node"], "Node"] = lambda x: x,
     sortkey: Optional[Callable[[Any], Any]] = None,
-    done: Optional[Set["IdentifiedNode"]] = None,
+    done: Optional[Set["Node"]] = None,
     dir: str = "down",
-) -> Optional[Tuple[IdentifiedNode, List[Any]]]:
+) -> Optional[Tuple[Node, List[Any]]]:
     """
     Return a nested list/tuple structure representing the tree
     built by the transitive property given, starting from the root given
@@ -442,12 +442,11 @@ def get_tree(
     done.add(root)
     tree = []
 
-    branches: Iterable[IdentifiedNode]
+    branches: Iterator[Node]
     if dir == "down":
         branches = graph.subjects(prop, root)
     else:
-        # type error: Incompatible types in assignment (expression has type "Iterable[Node]", variable has type "Iterable[IdentifiedNode]")
-        branches = graph.objects(root, prop)  # type: ignore[assignment]
+        branches = graph.objects(root, prop)
 
     for branch in branches:
         t = get_tree(graph, branch, prop, mapper, sortkey, done, dir)