anchor.diff:      //
       Right : Map<int<'Tag2>, int<'Tag1>>;
   }
  +
  
positive.code:             else
                  remove x bimap)
  
      // TODO
      // ofList, toList
      // ofArray, toArray
      // ofMap, toMap, tryOfMap
  
  
  
negative.code:         Map.fold folder state bimap.Left
  
      //
      [<CompiledName("FoldBack")>]
      let foldBack (folder : 'T1 -> 'T2 -> 'State -> 'State)
              (bimap : Bimap<'T1, 'T2>) (state : 'State) : 'State =
          // Preconditions
          checkNonNull "bimap" bimap
  
          Map.foldBack folder bimap.Left state
  
      //
      [<CompiledName("Filter")>]
      let filter (predicate : 'T1 -> 'T2 -> bool) (bimap : Bimap<'T1, 'T2>) : Bimap<'T1, 'T2> =
          // Preconditions
  