docs: function concatenateArguments(args1, args2) {
                  if (args1.params === undefined || args2.params === undefined)
                    return tr.b.concatenateObjects(args1, args2);
                  // Make an argument object to hold the combined params.
                  var args3 = {};
                  args3.params = tr.b.concatenateObjects(args1.params,
                                                         args2.params);
                  return tr.b.concatenateObjects(args1, args2, args3);
                }