def METHOD_NAME(self, acr, method, level=0, authn_authority=""):
    """
    Add a new authentication method.
    Assumes not more than one authentication method per type.
    :param acr: Add to what the authentication endpoint offers for this acr
    :param method: A identifier of the authentication method.
    :param level: security level, positive integers, 0 is lowest
    :return:
    """
    _info = {
        "ref": acr,
        "method": method,
        "level": level,
        "authn_auth": authn_authority,
    }
    self.next += 1
    _ref = str(self.next)
    self.db["info"][_ref] = _info
    try:
        self.db["key"][acr].append(_ref)
    except KeyError:
        self.db["key"][acr] = [_ref]