--- Store all inverse values for MM!B::reference
helper def : bByReference : Map(MM!C, MM!B) =
   MM!B.allInstances()->mappedBySingle(b | b.reference);

--- Define a helper attribute on MM!C for the inverse of MM!B::reference
helper context MM!C def : inverseReference : MM!B =
  thisModule.bByReference.get(self);