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

slideDuration: '0.2s'
      },
      medium: {
        fontSize: baseFontSize + 'px',
        lineHeight: 1.45,
        daySize: baseSpacing * 16 / 7 + 'px',
        slideDuration: '0.5s'
      },
      large: {
        fontSize: baseFontSize + fontScale + 'px',
        lineHeight: 1.11,
        daySize: baseSpacing * 32 / 7 + 'px',
        slideDuration: '0.8s'
      },
      icons: {
        previous: _grommetIcons.Previous,
        next: _grommetIcons.Next,
        small: {
          previous: _grommetIcons.FormPrevious,
          next: _grommetIcons.FormNext
        }
      }
    },
    carousel: {
      icons: {
        current: _grommetIcons.Subtract,
        next: _grommetIcons.Next,
        previous: _grommetIcons.Previous
        // color: undefined,
      }
    },
    checkBox: {

slideDuration: '0.8s'
      },
      icons: {
        previous: _grommetIcons.Previous,
        next: _grommetIcons.Next,
        small: {
          previous: _grommetIcons.FormPrevious,
          next: _grommetIcons.FormNext
        }
      }
    },
    carousel: {
      icons: {
        current: _grommetIcons.Subtract,
        next: _grommetIcons.Next,
        previous: _grommetIcons.Previous
        // color: undefined,
      }
    },
    checkBox: {
      border: {
        color: {
          dark: 'rgba(255, 255, 255, 0.5)',
          light: 'rgba(0, 0, 0, 0.15)'
        },
        radius: '4px',
        width: '2px'
      },
      check: {
        // color: { dark: undefined, light: undefined },
        width: '4px'
      },

axis = _this$state.axis,
        bounds = _this$state.bounds,
        interval = _this$state.interval,
        nextReference = _this$state.nextReference,
        previousReference = _this$state.previousReference,
        thickness = _this$state.thickness,
        values = _this$state.values;
    return _react["default"].createElement(_grommet.Grommet, {
      theme: _themes.grommet
    }, _react["default"].createElement(_grommet.Box, {
      pad: "large",
      direction: "row",
      gap: "medium"
    }, _react["default"].createElement(_grommet.Button, {
      hoverIndicator: true,
      icon: _react["default"].createElement(_grommetIcons.Previous, null),
      onClick: function onClick() {
        return _this2.setState({
          reference: previousReference
        });
      }
    }), _react["default"].createElement(_grommet.Box, {
      flex: true
    }, _react["default"].createElement(_grommet.Box, {
      direction: "row",
      justify: "end"
    }, Object.keys(intervalDays).map(function (_int) {
      return _react["default"].createElement(_grommet.Button, {
        key: _int,
        onClick: function onClick() {
          return _this2.setState({
            interval: _int

header: function header(_ref) {
      var currentDate = _ref.date,
          locale = _ref.locale,
          onPreviousMonth = _ref.onPreviousMonth,
          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, {