code: function (msgOrIds, payload, callback) {
          var ids = (external.is(msgOrIds).array) ? msgOrIds : messageIndex.query(msgOrIds);
  
          if (ids.length > 0) {
              var methods = [];
              var toDrop = [];
              for (var i = 0; i < ids.length; ++i) {
                  var msg = (external.is(msgOrIds).object) ? external.copy(msgOrIds) : external.copy(messageIndex.query(ids[i]));
                  var obj = handlers[ids[i]];
                  methods.push({
                      method: obj.handler,
                      params: [payload, msg]
                  });
  
                  if (obj.once === true) {
                      toDrop.push({
                          msg: msg,
                          handler: obj.handler
                      });
                  }
              }
  
              var execs = internal.executer(methods);
  
              for (var i = 0; i < toDrop.length; ++i) {
                  external(toDrop[i].msg).drop(toDrop[i].handler);
              }
  
              execs.parallel(callback);
          }
      }
docs: An explicit emit