format property
format specifies how the national (significant) number matched by pattern should be formatted. Using the same example as above, format could contain "$1 $2 $3", meaning that the number should be formatted as "20 7031 3000". Each $x are replaced by the numbers captured by group x in the regex specified by pattern.
Implementation
@$pb.TagNumber(2)
$core.String get format => $_getSZ(1);