
  [;1m-spec intersection(Set1, Set2) -> Set3[0m
  [;1m                      when[0m
  [;1m                          Set1 :: a_set(),[0m
  [;1m                          Set2 :: a_set(),[0m
  [;1m                          Set3 :: a_set().[0m

  Returns the intersection of [;;4mSet1[0m and [;;4mSet2[0m.
