anchor.diff:              
           | Br (_,_,_,_), Empty ->
               s
  -        | Lf (k, x), _ ->
  +        | Lf (k, _), _ ->
               if PatriciaMap.ContainsKey (k, t) then Empty
               else s
           | Empty, _ ->
  
positive.code:         | Br (_,_,_,_), Empty ->
              Empty
              
          | Lf (k, x), _ ->
              // Here, we always use the value from the left tree, so as long as the
              // right tree contains a binding with the same key, we just return the left tree.
              if PatriciaMap.ContainsKey (k, t) then s
  
negative.code:         | Br (p, m, s0, s1), Lf (k, y) ->
              if matchPrefix (k, p, m) then
                  if zeroBit (k, m) then
                      match PatriciaMap.Remove (k, s0) with
                      | Empty -> s1
                      | left ->
                          // OPTIMIZE : If left === s0 then return the map as-is instead of creating a new one.
                          Br (p, m, left, s1)
                  else
                      match PatriciaMap.Remove (k, s1) with
                      | Empty -> s0
                      | right ->
                          // OPTIMIZE : If right === s1 then return the map as-is instead of creating a new one.
  