SortSpec

{
    "backgroundColor": {},
    "backgroundColorStyle": {
        "rgbColor": {},
        "themeColor": "THEME_COLOR_TYPE_UNSPECIFIED"
    },
    "dataSourceColumnReference": {
        "name": "string"
    },
    "dimensionIndex": 0,
    "foregroundColor": {},
    "foregroundColorStyle": {
        "rgbColor": {},
        "themeColor": "THEME_COLOR_TYPE_UNSPECIFIED"
    },
    "sortOrder": "SORT_ORDER_UNSPECIFIED"
}