@classmethod
def get_class_field(cls, field_name):
    """
        Return the field object with the given name (for the class, the fields
        are in the "_redis_attr_%s" form)
        """
    if not cls.has_field(field_name):
        raise AttributeError('"%s" is not a field for the model "%s"' % (
            field_name, cls.__name__))
    return getattr(cls, '_redis_attr_%s' % field_name)
