public function getEdgeIndex($index)
    {
        if (!isset($this->edges[$index])) {
            throw new OutOfBoundsException('Invalid edge index');
        }
        return $this->edges[$index];
    }
public function getEdgeIndex($index)
    {
        if (!isset($this->edges[$index])) {
            throw new OutOfBoundsException('Invalid edge index');
        }
        return $this->edges[$index];
    }
public function getEdgeIndex ( $ index ) { if ( ! isset ( $ this -> edges [ $ index ] ) ) { throw new OutOfBoundsException ( 'Invalid edge index' ) ; } return $ this -> edges [ $ index ] ; }
return Edge at given array index

@param mixed $index
@throws OutOfBoundsException if the given index does not exist
@return Edge
return Edge at given array index