code: def append_flag_values(self, flag_values):
      
      for flag_name, flag in six.iteritems(flag_values._flags()):  # pylint: disable=protected-access
        # Each flags with short_name appears here twice (once under its
        # normal name, and again with its short name).  To prevent
        # problems (DuplicateFlagError) with double flag registration, we
        # perform a check to make sure that the entry we're looking at is
        # for its normal name.
        if flag_name == flag.name:
          try:
            self[flag_name] = flag
          except _exceptions.DuplicateFlagError:
            raise _exceptions.DuplicateFlagError.from_flag(
                flag_name, self, other_flag_values=flag_values)
docs: Appends flags registered in another FlagValues instance.
  
      Args:
        flag_values: FlagValues, the FlagValues instance from which to copy flags.