public function contains(Vertex $vertex)
	    {
	        if( $this->source == $vertex || 
	        	$this->target == $vertex)
	            return true;
	        return false;
	    }
public function contains(Vertex $vertex)
	    {
	        if( $this->source == $vertex || 
	        	$this->target == $vertex)
	            return true;
	        return false;
	    }
public function contains ( Vertex $ vertex ) { if ( $ this -> source == $ vertex || $ this -> target == $ vertex ) return true ; return false ; }
It verifies if the edge contains a given vertex.

@param vertex
@return true, if the edge contains the vertex; or false, on the contrary.
It verifies if the edge contains a given vertex .