public function previousY()
    {
        if ($this->previousYExists()) {
            $this->seekY($this->keyY()-1);
        } else {
            $this->y = null;
        }
        return $this;
    }
public function previousY()
    {
        if ($this->previousYExists()) {
            $this->seekY($this->keyY()-1);
        } else {
            $this->y = null;
        }
        return $this;
    }
public function previousY ( ) { if ( $ this -> previousYExists ( ) ) { $ this -> seekY ( $ this -> keyY ( ) - 1 ) ; } else { $ this -> y = null ; } return $ this ; }
Seek to current `y` less 1

@return  $this
Seek to current y less 1