@classmethod
def get_perm(cls, perm_type):
    """Converts permission type ("add") to permission name ("app.add_modelname")

        :param perm_type: "add", "change", etc., or custom value
        :type  perm_type: str
        :returns str:
        """
    return '%s.%s_%s' % (cls._meta.app_label, perm_type, cls._meta.model_name)
