'Return a dictionary with signal details.
Subclasses can invoke this method to retrieve information of the
resource signal for the specified transport.'

def _get_signal(self, signal_type=SIGNAL, multiple_signals=False):

    signal = None
    if self._signal_transport_cfn():
        signal = {'alarm_url': self._get_ec2_signed_url(signal_type=signal_type)}
    elif self._signal_transport_heat():
        signal = self._get_heat_signal_credentials()
        signal['alarm_url'] = self._get_heat_signal_url(project_id=self.stack.stack_user_project_id)
    elif self._signal_transport_temp_url():
        signal = {'alarm_url': self._get_swift_signal_url(multiple_signals=multiple_signals)}
    elif self._signal_transport_zaqar():
        signal = self._get_heat_signal_credentials()
        signal['queue_id'] = self._get_zaqar_signal_queue_id()
    elif self._signal_transport_none():
        signal = {}
    return signal
