code: public function selectHeaders($accept, $contentTypes)
      {
          $headers = [];
  
          $accept = $this->_selectAcceptHeader($accept);
          if ($accept !== null) {
              $headers['Accept'] = $accept;
          }
  
          $headers['Content-Type'] = $this->_selectContentTypeHeader($contentTypes);
          return $headers;
      }
docs: /*
  Selects headers for request
  @param string[] $accept type of header
  @param string[] $contentTypes types of content
  @return array