code: public function buildLinkPhase($bucket = '', $tag = '', $keep = false)
      {
          $this->setPhase('link', $this->assemblePhaseData($bucket, '', '', '', $tag), $keep);
  
          return $this;
      }
docs: buildReducePhase
  
  Allows you to define the Reduce Query Phase by using parameters
  
  @param string $bucket
  @param string $tag
  @param bool $keep
  
  @internal param string $key
  @internal param string $source
  @internal param string $language
  @return $this