Hmap.MakeSourceGet the value corresponding to this key, if it exists and belongs to the same key.
update ~inj k f m updates the value associated with k in m according to f (get ~inj k m). If the result is None, the binding associated with k is removed.
Find the value for the given key, which must be of the right type.
Is the given key in the map, with the right type?
All the bindings that come from the corresponding injection.