How to use the grommet-icons.Blank function in grommet-icons

header: function header(_ref2) {
      var currentDate = _ref2.date,
          locale = _ref2.locale,
          onNextMonth = _ref2.onNextMonth,
          nextInBound = _ref2.nextInBound;
      return _react["default"].createElement(_grommet.Box, {
        direction: "row",
        align: "center",
        justify: "between"
      }, _react["default"].createElement(_grommetIcons.Blank, null), _react["default"].createElement(_grommet.Heading, {
        level: 3,
        margin: "none"
      }, currentDate.toLocaleDateString(locale, {
        month: 'long',
        year: 'numeric'
      })), _react["default"].createElement(_grommet.Button, {
        disabled: !nextInBound,
        icon: _react["default"].createElement(_grommetIcons.Next, null),
        onClick: onNextMonth
      }));
    }
  })));

previousInBound = _ref.previousInBound;
      return _react["default"].createElement(_grommet.Box, {
        direction: "row",
        align: "center",
        justify: "between"
      }, _react["default"].createElement(_grommet.Button, {
        disabled: !previousInBound,
        icon: _react["default"].createElement(_grommetIcons.Previous, null),
        onClick: onPreviousMonth
      }), _react["default"].createElement(_grommet.Heading, {
        level: 3,
        margin: "none"
      }, currentDate.toLocaleDateString(locale, {
        month: 'long',
        year: 'numeric'
      })), _react["default"].createElement(_grommetIcons.Blank, null));
    }
  }), _react["default"].createElement(_grommet.Calendar, {