leadingDigits property
This field is populated only for countries or regions that share a country calling code. If a number matches this pattern, it could belong to this region. This is not intended as a replacement for IsValidForRegion since a matching prefix is insufficient for a number to be valid. Furthermore, it does not contain all the prefixes valid for a region - for example, 800 numbers are valid for all NANPA countries and are hence not listed here. This field should be a regular expression of the expected prefix match. It is used merely as a short-cut for working out which region a number comes from in the case that there is only one, so leading_digit prefixes should not overlap.
Implementation
@$pb.TagNumber(23)
$core.String get leadingDigits => $_getSZ(21);