anchor.diff:  
       member this.AddTerm termName term =
           let terms = Dictionary (terms, StringComparer.Ordinal)
  -        terms.Add (termName, term)
  +        terms.[termName] <- term
           ArchetypeId terms
   
       member this.RemoveTerm termName =
  
positive.code: open System.Threading.Tasks
  open Prime
  
  // TODO: 3D: make sure to use TryAdd in the appropriate places.
  // TODO: 3D: create try functions where applicable and do error-checking where not.
  
  /// Allows a value to always pass as equal with another of its same type.
  type [<CustomEquality; NoComparison; Struct>] 'a AlwaysEqual =
  
negative.code:             callback evt store
          boxableCallback :> obj
  
      member private this.RegisterEntityInternal archetypeId comps entityRef =
          let archetype =
              match archetypes.TryGetValue archetypeId with
              | (true, archetype) -> archetype
  