Membership Tests
•The Contains and Find operations are used to determine whether an element is in the map. Use Contains if all you need is a simple membership
test.
•Find returns a cursor as its result.
If the cursor object has
the distinguished value No_Element (or equivalently, the predicate Has_Element returns False), then the search failed and the key is not in the
map.
Otherwise, the cursor designates the key/element pair whose key matched.