src/marshmallow_sqlalchemy/convert.py
def _add_relationship_kwargs(self, kwargs, prop):
        """Add keyword arguments to kwargs (in-place) based on the passed in
        relationship `Property`.
        """
        nullable = True
        for pair in prop.local_remote_pairs:
            if not pair[0].nullable:
                if prop.uselist is True:
                    nullable = False
                break
        kwargs.update({"allow_none": nullable, "required": not nullable})
def _add_relationship_kwargs(self, kwargs, prop):
        """Add keyword arguments to kwargs (in-place) based on the passed in
        relationship `Property`.
        """
        nullable = True
        for pair in prop.local_remote_pairs:
            if not pair[0].nullable:
                if prop.uselist is True:
                    nullable = False
                break
        kwargs.update({"allow_none": nullable, "required": not nullable})
Add keyword arguments to kwargs (in-place) based on the passed in
        relationship `Property`.