Class Regex (3.5.0) 

Regex(mapping=None, *, ignore_unknown_fields=False, **kwargs)

Message defining a custom regular expression.

Attributes
Name Description
pattern str
Pattern defining the regular expression. Its syntax (https://github.com/google/re2/wiki/Syntax) can be found under the google/re2 repository on GitHub.
group_indexes Sequence[int]
(https://github.com/google/re2/wiki/Syntax) can be found under the The index of the submatch to extract as findings. When not specified, the entire match is returned. No more than 3 may be included.