code: public function message( $messageId )
      {
          $params = [
              'query' => [
  	            'apikey' =>  $this->apikey,
              ]
          ];
          $response = $this->client->get( 'messages/' . $messageId, $params );
          return $response->getBody();
      }
docs: Retrieves data about a specific message
  
  @param $messageId - The encoded ID of the message
  @return StreamInterface