protected function merge()
    {
        if (null === $this->merge) {
            $this->merge = new MergeBuilder($this);
        }

        return $this->merge;
    }
protected function merge()
    {
        if (null === $this->merge) {
            $this->merge = new MergeBuilder($this);
        }

        return $this->merge;
    }
protected function merge ( ) { if ( null === $ this -> merge ) { $ this -> merge = new MergeBuilder ( $ this ) ; } return $ this -> merge ; }
Gets the builder for merging rules.

@return MergeBuilder
Gets the builder for merging rules .