Add a docstring to the test.

Author: byrman

tests/test_mixin.py

@@ -10,6 +10,12 @@ class FooMixin:
 
 @pytest.mark.usefixtures("clear_sqlmodel")
 def test_mixin():
+    """Test SQLModel in combination with a mixin.
+
+    https://github.com/tiangolo/sqlmodel/issues/254
+
+    """
+
     class Hero(FooMixin, SQLModel, table=True):
         id: Optional[int] = Field(default=None, primary_key=True)
         name: str