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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def read_config_file(self, file_name):
 """ Reads a CWR grammar config file. :param file_name: name of the text file :return: the file's contents """

        with open(os.path.join(self.__path(), os.path.basename(file_name)),
                  'rt') as file_config:
            return self._parser.parseString(file_config.read())