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

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
            if your data set does not contain desired
            lower bound value.
        `,
        required: false,
        defaultValue: defaults.minValue,
        type: `number | 'auto'`,
        controlType: 'switchableRange',
        group: 'Base',

{
        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',
        scopes: ['api'],
        docScopes: '*',
        description: (
            <span>
                not required if using&nbsp;
                <code>&lt;ResponsiveHeatMap&nbsp;/&gt;</code>.
            </span>
        ),