How to use the @nivo/geo.GeoMapDefaultProps.borderColor function in @nivo/geo

controlType: 'range',
        controlGroup: 'Style',
        controlOptions: {
            unit: 'px',
            min: 0,
            max: 10,
            step: 0.5,
        },
    },
    {
        key: 'borderColor',
        scopes: '*',
        description: 'Method to compute border color.',
        type: '{string|Function}',
        required: false,
        default: GeoMapDefaultProps.borderColor,
        controlType: 'color',
        controlGroup: 'Style',
        controlOptions: {
            withCustomColor: true,
        },
    },
    {
        key: 'enableGraticule',
        scopes: '*',
        description: 'Enable meridians and parallels, useful for showing projection distortion.',
        type: '{boolean}',
        required: false,
        default: GeoMapDefaultProps.enableGraticule,
        controlType: 'switch',
        controlGroup: 'Graticule',
    },

help: 'Control border width.',
        type: 'number',
        required: false,
        defaultValue: GeoMapDefaultProps.borderWidth,
        controlType: 'lineWidth',
        group: 'Style',
        controlOptions: {
            step: 0.5,
        },
    },
    {
        key: 'borderColor',
        help: 'Method to compute border color.',
        type: 'string | object | Function',
        required: false,
        defaultValue: GeoMapDefaultProps.borderColor,
        controlType: 'inheritedColor',
        group: 'Style',
    },
    {
        key: 'enableGraticule',
        help: 'Enable meridians and parallels, useful for showing projection distortion.',
        type: 'boolean',
        required: false,
        defaultValue: GeoMapDefaultProps.enableGraticule,
        controlType: 'switch',
        group: 'Graticule',
    },
    {
        key: 'graticuleLineWidth',
        help: 'Control meridians and parallel lines width.',
        type: 'number',