Update field with values from its parent schema. Called by
            :meth:`_bind_field<marshmallow.Schema._bind_field>`.

        :param str field_name: Field name set in schema.
        :param Schema schema: Parent schema.

def _bind_to_schema(self, field_name, schema):
        """Update field with values from its parent schema. Called by
            :meth:`_bind_field<marshmallow.Schema._bind_field>`.

        :param str field_name: Field name set in schema.
        :param Schema schema: Parent schema.
        """
        self.parent = self.parent or schema
        self.name = self.name or field_name