removeQuotationMark function
Implementation
String removeQuotationMark(String input) {
  if ((input.startsWith(_singleQuote) && input.endsWith(_singleQuote)) ||
      (input.startsWith(_doubleQuote) && input.endsWith(_doubleQuote))) {
    input = input.substring(1, input.length - 1);
  }
  return input;
}