def _populate_validated_data_with_sub_field_data(self, validated_data):
        """
        Move field data nested in `ModelSubSerializer` fields back into the
        overall validated data dict.
        """
        for fieldname, field in self.get_fields().items():
            if isinstance(field, ModelSubSerializer):
                field_data = validated_data.pop(fieldname, None)
                if field_data:
                    validated_data.update(field_data)
Move field data nested in `ModelSubSerializer` fields back into the
        overall validated data dict.