code: def StrPrefixOf(prefix, input_string):
      
      return re.match(r'^' + prefix.value, input_string.value) is not None
docs: Return True if the concrete value of the input_string starts with prefix
      otherwise false.
  
      :param prefix: prefix we want to check
      :param input_string: the string we want to check
  
      :return: True if the input_string starts with prefix else false