def delete(obj, key=None):
    """
    Delete a single key if specified, or all env if key is none
    :param obj: settings object
    :param key: key to delete from store location
    :return: None
    """
    client = StrictRedis(**obj.REDIS_FOR_DYNACONF)
    holder = obj.get("ENVVAR_PREFIX_FOR_DYNACONF")
    if key:
        client.hdel(holder.upper(), key.upper())
        obj.unset(key)
    else:
        keys = client.hkeys(holder.upper())
        client.delete(holder.upper())
        obj.unset_all(keys)