code: public function update($partialDocument, $id, array $options = array()) {
          $url = $this->buildUrl(array($this->type, $id), $options);
  
          return $this->call($url, "POST", array('doc' => $partialDocument));
      }
docs: Update a part of a document
  
  @return array
  
  @param array $partialDocument
  @param mixed $id
  @param array $options