code: function () {
                              // get message reply
                              message = fn( data );
                              // check message type
                              mtype = message[ 0 ];
                              // check for message and pmessage
                              // get the message and don't pop command
                              if ( ~ mtype.indexOf( 'message' ) ) return me.emit( 'message', message, Formatters.message );
                              if ( ! cmd ) {
                                  // command is undefined, a message was received
                                  msubs = message[ 2 ];
                                  // update current pubsub status
                                  subs = bilanx.update( mtype, msubs );
                                  me.emit( 'message', message, Formatters.message );
                                  return subs === 0 ? me.emit( 'shutup' ) : null;
                              }
                              // command could be a subscription, then a message reply to a (un)subscription
                              return cmd.isSubscription ? getReplyMessages() : getReply();
                          }
docs: get queue head