Returns a lazy, access elements only when needed view of the current
public function lazy(): HH\Rx\KeyedIterable<arraykey, Tv>;
Normally, memory is allocated for all of the elements of an
a lazy view, memory is allocated for an element only when needed or used
in a calculation like in
HH\Rx\KeyedIterable<arraykey, Tv>- an
KeyedIterablerepresenting the lazy view into the current
ImmSet, where the keys are the same as the values.
Set::lazy for usage examples.