code: def DEFINE_alias(name, original_name, flag_values=FLAGS, module_name=None):  # pylint: disable=g-bad-name
    
    if original_name not in flag_values:
      raise UnrecognizedFlagError(original_name)
    flag = flag_values[original_name]
  
    class _Parser(ArgumentParser):
      """The parser for the alias flag calls the original flag parser."""
  
      def parse(self, argument):
        flag.parse(argument)
        return flag.value
  
    class _FlagAlias(Flag):
      """Overrides Flag class so alias value is copy of original flag value."""
  
      @property
      def value(self):
        return flag.value
  
      @value.setter
      def value(self, value):
        flag.value = value
  
    help_msg = 'Alias for --%s.' % flag.name
    # If alias_name has been used, gflags.DuplicatedFlag will be raised.
    DEFINE_flag(_FlagAlias(_Parser(), flag.serializer, name, flag.default,
                           help_msg, boolean=flag.boolean),
                flag_values, module_name)
docs: Defines an alias flag for an existing one.
  
    Args:
      name: A string, name of the alias flag.
      original_name: A string, name of the original flag.
      flag_values: FlagValues object with which the flag will be registered.
      module_name: A string, the name of the module that defines this flag.
  
    Raises:
      gflags.FlagError:
        UnrecognizedFlagError: if the referenced flag doesn't exist.
        DuplicateFlagError: if the alias name has been used by some existing flag.