def credentials(self):
        """
        :rtype: twilio.rest.notify.v1.credential.CredentialList
        """
        if self._credentials is None:
            self._credentials = CredentialList(self)
        return self._credentials
def credentials ( self ) : if self . _credentials is None : self . _credentials = CredentialList ( self ) return self . _credentials
:rtype: twilio.rest.notify.v1.credential.CredentialList