underscore method
Converts a camelized string into all lower case separated by underscores.
Implementation
String underscore() {
if (this == null) {
throw ArgumentError('string: $this');
}
if (this!.isEmpty) {
return '';
}
return this!
.replaceAllMapped(RegExp(r'([A-Z])'), (match) => '_${match[1]}')
.toLowerCase();
}