format static method
Implementation
static String format(String cpf, {bool anywhere = false}) {
if (anywhere == false && !isValid(cpf)) {
throw AssertionError('CPF inválido!');
}
var regExp = RegExp(r'^(\d{3})(\d{3})(\d{3})(\d{2})$');
return strip(cpf).replaceAllMapped(regExp, (Match m) => '${m[1]}.${m[2]}.${m[3]}-${m[4]}');
}