code: public HashSet<UserTypeVal> allInitialDataTypes() {
          if (allInitialDataTypes == null) {
              // Would be cleaner if we could call scala's apply method here, but it isn't part of a HashSet companion
              // object -- instead it lives in GenericCompanion, and it's unclear now to get to it from Java.
              allInitialDataTypes = new HashSet<>();
              allInitialDataTypes = allInitialDataTypes.$plus(UserType.ADMIN);
          }
          return allInitialDataTypes;
      }
docs: All data types that can be the first node added to a graph.
  @return Set of types