Returns a set containing the keys of this map.
Examples:
[1: 'a', 2: 'b', 3: 'c'].keys() returns set([1, 2, 3]).
[1: 'a', 2: 'b', 3: 'c'].keys()
set([1, 2, 3])
map<K,V>().keys() returns set() (where K and V are valid types).
map<K,V>().keys()
set()
K
V
0.6.0