diff --git a/sqlmodel/ext/asyncio/session.py b/sqlmodel/ext/asyncio/session.py
index 80267b2..e6b176a 100644
--- a/sqlmodel/ext/asyncio/session.py
+++ b/sqlmodel/ext/asyncio/session.py
@@ -1,9 +1,11 @@
-from typing import Any, Mapping, Optional, Sequence, TypeVar, Union
+from typing import Any, Dict, Mapping, Optional, Sequence, Type, TypeVar, Union
 
 from sqlalchemy import util
 from sqlalchemy.ext.asyncio import AsyncSession as _AsyncSession
 from sqlalchemy.ext.asyncio import engine
 from sqlalchemy.ext.asyncio.engine import AsyncConnection, AsyncEngine
+from sqlalchemy.orm import Mapper
+from sqlalchemy.sql.expression import TableClause
 from sqlalchemy.util.concurrency import greenlet_spawn
 from sqlmodel.sql.base import Executable
 
@@ -14,13 +16,18 @@ from ...sql.expression import Select
 _T = TypeVar("_T")
 
 
+BindsType = Dict[
+    Union[Type[Any], Mapper[Any], TableClause, str], Union[AsyncEngine, AsyncConnection]
+]
+
+
 class AsyncSession(_AsyncSession):
     sync_session: Session
 
     def __init__(
         self,
         bind: Optional[Union[AsyncConnection, AsyncEngine]] = None,
-        binds: Optional[Mapping[object, Union[AsyncConnection, AsyncEngine]]] = None,
+        binds: Optional[BindsType] = None,
         **kw: Any,
     ):
         # All the same code of the original AsyncSession
diff --git a/sqlmodel/main.py b/sqlmodel/main.py
index 141005f..56ba414 100644
--- a/sqlmodel/main.py
+++ b/sqlmodel/main.py
@@ -61,6 +61,9 @@ def __dataclass_transform__(
 
 
 class FieldInfo(PydanticFieldInfo):
+
+    nullable: Union[bool, PydanticUndefinedType]
+
     def __init__(self, default: Any = PydanticUndefined, **kwargs: Any) -> None:
         primary_key = kwargs.pop("primary_key", False)
         nullable = kwargs.pop("nullable", PydanticUndefined)
@@ -587,7 +590,7 @@ class SQLModel(BaseModel, metaclass=SQLModelMetaclass, registry=default_registry
 
 
 def _is_field_noneable(field: FieldInfo) -> bool:
-    if getattr(field, "nullable", PydanticUndefined) is not PydanticUndefined:
+    if not isinstance(field.nullable, PydanticUndefinedType):
         return field.nullable
     if not field.is_required():
         default = getattr(field, "original_default", field.default)
diff --git a/sqlmodel/orm/session.py b/sqlmodel/orm/session.py
index 9a07956..dab26c3 100644
--- a/sqlmodel/orm/session.py
+++ b/sqlmodel/orm/session.py
@@ -12,9 +12,7 @@ from typing import (
 
 from sqlalchemy import util
 from sqlalchemy.orm import Mapper as _Mapper
-from sqlalchemy.orm import Query as _Query
 from sqlalchemy.orm import Session as _Session
-from sqlalchemy.sql.base import Executable as _Executable
 from sqlalchemy.sql.selectable import ForUpdateArg as _ForUpdateArg
 from sqlmodel.sql.expression import Select, SelectOfScalar
 
@@ -81,56 +79,6 @@ class Session(_Session):
             return results.scalars()  # type: ignore
         return results  # type: ignore
 
-    def execute(
-        self,
-        statement: _Executable,
-        params: Optional[Union[Mapping[str, Any], Sequence[Mapping[str, Any]]]] = None,
-        execution_options: Mapping[str, Any] = util.EMPTY_DICT,
-        bind_arguments: Optional[Dict[str, Any]] = None,
-        _parent_execute_state: Optional[Any] = None,
-        _add_event: Optional[Any] = None,
-        **kw: Any,
-    ) -> Result[Any]:
-        """
-        🚨 You probably want to use `session.exec()` instead of `session.execute()`.
-
-        This is the original SQLAlchemy `session.execute()` method that returns objects
-        of type `Row`, and that you have to call `scalars()` to get the model objects.
-
-        For example:
-
-        ```Python
-        heroes = session.execute(select(Hero)).scalars().all()
-        ```
-
-        instead you could use `exec()`:
-
-        ```Python
-        heroes = session.exec(select(Hero)).all()
-        ```
-        """
-        return super().execute(  # type: ignore
-            statement,
-            params=params,
-            execution_options=execution_options,
-            bind_arguments=bind_arguments,
-            _parent_execute_state=_parent_execute_state,
-            _add_event=_add_event,
-            **kw,
-        )
-
-    def query(self, *entities: Any, **kwargs: Any) -> "_Query[Any]":
-        """
-        🚨 You probably want to use `session.exec()` instead of `session.query()`.
-
-        `session.exec()` is SQLModel's own short version with increased type
-        annotations.
-
-        Or otherwise you might want to use `session.execute()` instead of
-        `session.query()`.
-        """
-        return super().query(*entities, **kwargs)  # type: ignore
-
     def get(
         self,
         entity: Union[Type[_TSelectParam], "_Mapper[_TSelectParam]"],
@@ -152,3 +100,34 @@ class Session(_Session):
             execution_options=execution_options,
             bind_arguments=bind_arguments,
         )
+
+
+Session.query.__doc__ = """
+🚨 You probably want to use `session.exec()` instead of `session.query()`.
+
+`session.exec()` is SQLModel's own short version with increased type
+annotations.
+
+Or otherwise you might want to use `session.execute()` instead of
+`session.query()`.
+"""
+
+
+Session.execute.__doc__ = """
+🚨 You probably want to use `session.exec()` instead of `session.execute()`.
+
+This is the original SQLAlchemy `session.execute()` method that returns objects
+of type `Row`, and that you have to call `scalars()` to get the model objects.
+
+For example:
+
+```Python
+heroes = session.execute(select(Hero)).scalars().all()
+```
+
+instead you could use `exec()`:
+
+```Python
+heroes = session.exec(select(Hero)).all()
+```
+"""
diff --git a/sqlmodel/sql/expression.py b/sqlmodel/sql/expression.py
index 8cb2309..a0ac1bd 100644
--- a/sqlmodel/sql/expression.py
+++ b/sqlmodel/sql/expression.py
@@ -35,14 +35,6 @@ class SelectOfScalar(_Select[Tuple[_TSelect]], Generic[_TSelect]):
     inherit_cache = True
 
 
-# This is not comparable to sqlalchemy.sql.selectable.ScalarSelect, that has a different
-# purpose. This is the same as a normal SQLAlchemy Select class where there's only one
-# entity, so the result will be converted to a scalar by default. This way writing
-# for loops on the results will feel natural.
-class SelectOfScalar(_Select, Generic[_TSelect]):
-    inherit_cache = True
-
-
 if TYPE_CHECKING:  # pragma: no cover
     from ..main import SQLModel
 
diff --git a/sqlmodel/sql/expression.py.jinja2 b/sqlmodel/sql/expression.py.jinja2
index 55f4a1a..4284543 100644
--- a/sqlmodel/sql/expression.py.jinja2
+++ b/sqlmodel/sql/expression.py.jinja2
@@ -30,12 +30,6 @@ class Select(_Select[Tuple[_TSelect]], Generic[_TSelect]):
 class SelectOfScalar(_Select[Tuple[_TSelect]], Generic[_TSelect]):
     inherit_cache = True
 
-# This is not comparable to sqlalchemy.sql.selectable.ScalarSelect, that has a different
-# purpose. This is the same as a normal SQLAlchemy Select class where there's only one
-# entity, so the result will be converted to a scalar by default. This way writing
-# for loops on the results will feel natural.
-class SelectOfScalar(_Select, Generic[_TSelect]):
-    inherit_cache = True
 
 if TYPE_CHECKING:  # pragma: no cover
     from ..main import SQLModel