convert method
override
 Converts input and returns the result of the conversion.
Implementation
String convert(List<int> input) {
  if (input.isEmpty) return "";
  var encoder = _Base64Encoder(_urlSafe);
  var buffer = encoder.encode(input, 0, input.length, true)!;
  return String.fromCharCodes(buffer);
}
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Licensed under the Creative Commons Attribution-ShareAlike License v4.0.
    https://api.dart.dev/stable/2.13.0/dart-convert/Base64Encoder/convert.html