How to use the @nivo/heatmap.HeatMapDefaultProps.indexBy function in @nivo/heatmap

required: true,
    },
    {
        key: 'indexBy',
        group: 'Base',
        help: 'Key to use to index the data.',
        description: `
            Key to use to index the data,
            this key must exist in each data item.
            You can also provide a function which will
            receive the data item and must return
            the desired index
        `,
        type: 'string | Function',
        required: false,
        defaultValue: defaults.indexBy,
    },
    {
        key: 'keys',
        group: 'Base',
        help: 'Keys to use to determine each serie.',
        type: 'string[]',
        required: false,
        defaultValue: defaults.keys,
    },
    {
        key: 'minValue',
        help: 'Minimum value.',
        description: `
            Minimum value.
            If 'auto', will pick the lowest value
            in the provided data set. Should be overriden

export default [
    {
        key: 'data',
        scopes: '*',
        description: 'Chart data.',
        type: '{Array.}',
        required: true,
    },
    {
        key: 'indexBy',
        scopes: '*',
        description:
            'Key to use to index the data, this key must exist in each data item. You can also provide a function which will receive the data item and must return the desired index',
        type: '{string|Function}',
        required: false,
        default: defaults.indexBy,
    },
    {
        key: 'keys',
        scopes: '*',
        description: 'Keys to use to determine each serie.',
        type: '{Array.}',
        required: false,
        default: defaults.keys,
    },
    /*——————————————————————————————————————————————————————————————————————————

      Base

    ————————————————————————————————————————————————————————————————————————————*/
    {
        key: 'width',