code: function _fillInputCheckbox(element, value, next) {
          var onIsSelected = chainAndErrorCallback.call(this, function (selected, next) {
              //ensure boolean
              value = !!value;
              if (value === selected) {
                  // nothing to do
                  return next();
              }
              element.click(next);
          }, next);
          element.isSelected(onIsSelected);
      }
docs: check or uncheck given checkbox