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Solve the following problem using Python, implementing the functions described below, one line at a time
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<USER_TASK:>
Description:
 def register_multi_flags_validator(flag_names, multi_flags_checker, message='Flags validation failed', flag_values=FLAGS):
 """Adds a constraint to multiple flags. The constraint is validated when flags are initially parsed, and after each change of the corresponding flag's value. Args: flag_names: [str], a list of the flag names to be checked. multi_flags_checker: callable, a function to validate the flag. input - dictionary, with keys() being flag_names, and value for each key being the value of the corresponding flag (string, boolean, etc). output - Boolean. Must return True if validator constraint is satisfied. If constraint is not satisfied, it should either return False or raise gflags.ValidationError. message: Error text to be shown to the user if checker returns False. If checker raises gflags.ValidationError, message from the raised error will be shown. flag_values: An optional FlagValues instance to validate against. Raises: AttributeError: If a flag is not registered as a valid flag name. """

  v = gflags_validators.MultiFlagsValidator(
      flag_names, multi_flags_checker, message)
  _add_validator(flag_values, v)