@classmethod
def _add_dynamic_field_to_model(cls, field, field_name):
    """
        Add a copy of the DynamicField "field" to the current class and its
        subclasses using the "field_name" name
        """
    new_field = field._create_dynamic_version()
    new_field.name = field_name
    new_field._attach_to_model(cls)
    setattr(cls, '_redis_attr_%s' % field_name, new_field)
    for subclass in cls.__subclasses__():
        subclass._add_dynamic_field_to_model(field, field_name)
    return new_field
