--- a/base.py	2021-04-03 16:36:30.201594994 -0400
+++ b/base.py	2021-04-03 16:38:26.404475025 -0400
@@ -1,3 +1,15 @@
+from sqlalchemy import Column
+from sqlalchemy import Integer
+from sqlalchemy import String
 from sqlalchemy.orm import declarative_base
+from sqlalchemy.orm import declarative_mixin
+from sqlalchemy.orm import Mapped

 Base = declarative_base()
+
+
+@declarative_mixin
+class Mixin:
+    mixed = Column(String)
+
+    b_int: Mapped[int] = Column(Integer)
--- a/one.py	2021-04-03 16:37:17.906956282 -0400
+++ b/one.py	2021-04-03 16:38:33.469528528 -0400
@@ -1,13 +1,15 @@
 from sqlalchemy import Column
 from sqlalchemy import Integer
+
 from .base import Base
+from .base import Mixin


-class One(Base):
+class One(Mixin, Base):
     __tablename__ = "one"
     id = Column(Integer, primary_key=True)


-o1 = One(id=5)
+o1 = One(id=5, mixed="mixed", b_int=5)

 One.id.in_([1, 2])