/**
* Signal the given execution if it is in a wait state.
*
* @param Execution $execution
* @param string $signal
* @param array $variables
* @param array $delegation
*/
public function signal(Execution $execution, $signal = NULL, array $variables = [], array $delegation = [])
{
if ($execution->isWaiting()) {
$execution->signal($signal, $variables, $delegation);
}
}
