/**
  * Add an element.
  *
  * @param string                         $id
  * @param GraphCommons\Graph\GraphEntity $graphEntity
  */
 public final function add($id, GraphEntity $graphEntity)
 {
     parent::set($id, $graphEntity);
     return $this;
 }
 /**
  * Add an element.
  *
  * @param string                    $id
  * @param GraphCommons\Graph\Signal $signal
  */
 public final function add(Signal $signal)
 {
     parent::set($this->count(), $signal);
     return $this;
 }