Unparses all flags to the point before any FLAGS(argv) was called.

def unparse_flags(self):
    """Unparses all flags to the point before any FLAGS(argv) was called."""
    for f in self._flags().values():
      f.unparse()
    # We log this message before marking flags as unparsed to avoid a
    # problem when the logging library causes flags access.
    logging.info('unparse_flags() called; flags access will now raise errors.')
    self.__dict__['__flags_parsed'] = False
    self.__dict__['__unparse_flags_called'] = True