public ReturnValue dropNullable() {
      if (!myNullability.contains(Nullability.NULLABLE)) return this;
      EnumSet<Nullability> copy = EnumSet.copyOf(myNullability);
      copy.remove(Nullability.NULLABLE);
      copy.add(Nullability.UNKNOWN);
      return new ReturnValue(copy, myCalledMethod, myRanges);
    }
public ReturnValue dropNullable()