How to use the @nivo/bar.BarDefaultProps.borderColor function in @nivo/bar

type: 'number',
        required: false,
        defaultValue: defaults.borderWidth,
        controlType: 'lineWidth',
        group: 'Style',
    },
    {
        key: 'borderColor',
        help: 'Method to compute border color.',
        description: `
            how to compute border color,
            [see dedicated documentation](self:/guides/colors).
        `,
        type: 'string | object | Function',
        required: false,
        defaultValue: defaults.borderColor,
        controlType: 'inheritedColor',
        group: 'Style',
    },
    ...defsProperties('Style', ['svg']),
    {
        key: 'layers',
        flavors: ['svg'],
        help: 'Defines the order of layers.',
        description: `
            Defines the order of layers, available layers are:
            \`grid\`, \`axes\`, \`bars\`, \`markers\`, \`legends\`.

            You can also use this to insert extra layers to the chart,
            this extra layer must be a function which will receive
            the chart computed data and must return a valid SVG
            element.