Registers a flag whose value can be a list strings from enum_values.

Use the flag on the command line multiple times to place multiple enum values into the list. The 'default' may be a single string (which will be converted into a single-element list) or a list of strings.

name str, the flag name.
default Union[Iterable[Text], Text, None], the default value of the flag; see DEFINE_multi.
enum_values [str], a non-empty list of strings with the possible values for the flag.
help str, the help message.
flag_values FlagValues, the FlagValues instance with which the flag will be registered. This should almost never need to be overridden.
case_sensitive Whether or not the enum is to be case-sensitive.
**args Dictionary with extra keyword args that are passed to the Flag init.

a handle to defined flag.