mergeIterables function
Merges two iterables into one iterable.
Implementation
Iterable<dynamic> mergeIterables(dynamic a, dynamic b) {
final aa = a is Iterable ? a.nonNulls : Iterable.generate(1, (_) => a);
final bb = b is Iterable ? b.nonNulls : Iterable.generate(1, (_) => b);
return aa.followedBy(bb);
}