code: protected function makeMessageOptions(array $incoming, $endSession = false)
      {
          $options = [
              'endSession' => $endSession,
              'returnXml' => $this->returnResultXml
          ];
  
          if (array_key_exists('endSession', $incoming)) {
              $options['endSession'] = $incoming['endSession'];
          }
  
          if (array_key_exists('returnXml', $incoming)) {
              $options['returnXml'] = $incoming['returnXml'];
          }
  
          return $options;
      }
docs: Make message options
  
  Message options are meta options when sending a message to the amadeus web services
  - 'endSession' (if stateful) : should we end the current session after sending this call?
  - 'returnXml' : Should we return the XML string in the Result::responseXml property?
  (this overrides the default setting returnXml in the Amadeus\Client\Params for a single message)
  
  @param array $incoming The Message options chosen by the caller - if any.
  @param bool $endSession Switch if you want to terminate the current session after making the call.
  @return array