Convert raw input value of the field.

        :param object value:
        :rtype object:

def _converter(self, value):
        """Convert raw input value of the field.

        :param object value:
        :rtype object:
        """
        if type(value) is not self.related_model_cls.Collection:
            value = self.related_model_cls.Collection([
                self._get_model_instance(self.related_model_cls, item)
                for item in value])
        return value