code: public CoreGraphAlgorithms init(String label, String rel)  {
          TokenRead token = ktx.tokenRead();
          int labelId = token.nodeLabel(label);
          int relTypeId = token.relationshipType(rel);
          loadNodes(labelId, relTypeId);
          loadRels(labelId, relTypeId);
          return this;
      }
docs: keep threads with open worker-tx for reads