anchor.diff:              None
           | Lf (j, listMap) ->
               if j = keyHash then
  -                NonEmptyAssociationList.TryFind (key, listMap)
  +                ListMap.TryFind (key, listMap)
               else None
           | Br (p, m, t0, t1) ->
               PatriciaHashMap.TryFind (
  
positive.code:         | Br (p, m, s0, s1), Lf (k, y) ->
              if matchPrefix (k, p, m) then
                  if zeroBit (k, m) then
                      match PatriciaHashMap.Delete (k, s0) with
                      | Empty -> s1
                      | left ->
                          Br (p, m, left, s1)
                  else
                      match PatriciaHashMap.Delete (k, s1) with
                      | Empty -> s0
                      | right ->
                          Br (p, m, s0, right)
  
negative.code: 
          | Empty, _ ->
              Empty
  
      /// Compute the difference of two PatriciaMaps.
      static member Difference (s, t) : PatriciaHashMap<'Key, 'T> =
  