code: function (caller_args, caller_result) {
              if (!this.enabled())
                  return undefined;
              var args = [];
              if (this.async()) {
                  args.push(function (value) {
                      if (typeof caller_result === "function")
                          caller_result(value);
                  });
              }
              args = _cs.concat(args, this.args(), caller_args);
              return this.func().apply(this.ctx(), args);
          }
docs: /*  method: execute the command