Documentation updates- remove new mixins from ref, add some comments

Author: pamelafox

docs/api.rst

@@ -36,8 +36,7 @@ Metaclass mixins (SQLAlchemy 1.x)
 ---------------------------------
 
 If your code uses the SQLAlchemy 1.x API (the default for code that doesn't specify a ``model_class``),
-then these mixins are automatically applied to the ``Model`` class. They can also be used
-directly to create custom metaclasses. See :doc:`customizing` for more information.
+then these mixins are automatically applied to the ``Model`` class.
 
 .. autoclass:: DefaultMeta
 
@@ -46,18 +45,6 @@ directly to create custom metaclasses. See :doc:`customizing` for more informati
 .. autoclass:: NameMetaMixin
 
 
-Base class mixins (SQLAlchemy 2.x)
-----------------------------------
-
-If your code uses the SQLAlchemy 2.x API by passing a subclass of ``DeclarativeBase``
-or ``DeclarativeBaseNoMeta`` as the ``model_class``, then the following classes
-are automatically added as additional base classes.
-
-.. autoclass:: BindMixin
-
-.. autoclass:: NameMixin
-
-
 Session
 -------
 

src/flask_sqlalchemy/model.py

@@ -300,8 +300,11 @@ def should_set_tablename(cls: type) -> bool:
             base is cls
             or base.__dict__.get("__abstract__", False)
             or not (
+                # SQLAlchemy 1.x
                 isinstance(base, sa_orm.DeclarativeMeta)
+                # 2.x: DeclarativeBas uses this as metaclass
                 or isinstance(base, sa_orm.decl_api.DeclarativeAttributeIntercept)
+                # 2.x: DeclarativeBaseNoMeta doesn't use a metaclass
                 or issubclass(base, sa_orm.DeclarativeBaseNoMeta)
             )
         )