thenBy method
Returns a new list with all elements sorted according to previously
defined order and natural sort order of the values returned by specified
selector
function.
Note: The actual sorting is performed when an element is accessed for the first time.
Implementation
SortedList<E> thenBy(Comparable Function(E element) selector) {
return SortedList<E>.withSelector(this, selector, 1, _comparator);
}