Getting invalid json error from ChatGPT API due to special characters.

Hello, I have a custom function that converts a nested json list to a string. I send this string to the ChatGPT API for summarisation.

A problem that I am encountering is that when there are special characters present in the nested json list, I get an invalid json error from the ChatGPT API.

The complete custom function is provided below:

import 'dart:convert';
import 'dart:math' as math;

import 'package:flutter/material.dart';
import 'package:google_fonts/google_fonts.dart';
import 'package:intl/intl.dart';
import 'package:timeago/timeago.dart' as timeago;
import '/flutter_flow/lat_lng.dart';
import '/flutter_flow/place.dart';
import '/flutter_flow/uploaded_file.dart';
import '/flutter_flow/custom_functions.dart';
import '/auth/firebase_auth/auth_util.dart';

String? jsonListToString(
  List<dynamic>? jsonList,
  String? separator,
) {
  /// MODIFY CODE ONLY BELOW THIS LINE

  if (jsonList == null || separator == null) {
    return null;
  }
  final List<String> stringList = [];
  for (final dynamic item in jsonList) {
    if (item is List) {
      final String? nestedListString = jsonListToString(item, separator);
      if (nestedListString != null) {
        stringList.add(
            nestedListString.replaceAll('"', '\\"').replaceAll("\\", "\\\\"));
      }
    } else if (item is Map) {
      final String? nestedMapString =
          jsonEncode(item).replaceAll('"', '\\"').replaceAll("\\", "\\\\");
      if (nestedMapString != null) {
        stringList.add(nestedMapString);
      }
    } else {
      final String? itemString =
          item?.toString().replaceAll('"', '\\"').replaceAll("\\", "\\\\");
      if (itemString != null) {
        stringList.add(itemString);
      }
    }
  }

  return stringList.join(separator);

  /// MODIFY CODE ONLY ABOVE THIS LINE
}

Been stuck on this for a while, would appreciate any help with this. Thanks!