code: public function toXML( XMLWriter $XMLWriter )
      {
          if ($this->sessionId) {
              $XMLWriter->writeElement( 'SessionID', $this->sessionId );
          } else {
              throw new RequiredFieldException( 'Field SessionID of the FingerPrint object is required' );
          }
      }
docs: @param  \XMLWriter $XMLWriter
  
  @throws \RodrigoPedra\ClearSaleID\Exception\RequiredFieldException