Clear conditional formatting using Advanced Sheet Service in Google Apps script

[Valorx User]

I am trying to delete conditional formatting of a range using below code:

var sheet = range.getSheet();
var address = range.getA1Notation();

var conditionalFormatRules = sheet.getConditionalFormatRules();
var conditionalFormatRule = [];
var sheetId = sheet.getSheetId();
for (let index = 0; index < conditionalFormatRules.length; index++) {
    let ranges = conditionalFormatRules[index].getRanges();
    for (let j = 0; j < ranges.length; j++) {
        if (ranges[j].getA1Notation() == address) {
            conditionalFormatRule.push({
                "deleteConditionalFormatRule": {
                    "index": index,
                    "sheetId": sheetId
                }
            });
        }
    }
}

if (conditionalFormatRule.length > 0) {
    var spreadsheet = SpreadsheetApp.getActive();
    var ssId = spreadsheet.getId();
    var format_req = {
        "requests": conditionalFormatRule
    };
    Sheets.Spreadsheets.batchUpdate(format_req, ssId);
}

But it fails with the following exception:

{ [GoogleJsonResponseException: API call to sheets.spreadsheets.batchUpdate failed with error: Invalid requests[8].deleteConditionalFormatRule: No conditional format on sheet: 1876237346 at index: 8] name: 'GoogleJsonResponseException', details: { message: 'Invalid requests[8].deleteConditionalFormatRule: No conditional format on sheet: .... at index: 8', code: 400 } }

It says there is no conditional formatting at index: 8 but there are 11 conditional format rules for that particular range (confirmed by logging the conditional formatting rules)

I want to delete all the conditional formatting rules for a particular range if there is any better way please suggest.

Thanks in advance.