code: private InternalNodeState combineInternalNodeStates(InternalNodeState inState, ExternalNode3 externalNode) {
  
          ExternalNode3 n1 = inState.getExternalNode();
  
          ExternalNode3 n = combineExternalNodes(n1, externalNode);
  
          return new InternalNodeState(n);
      }
docs: Combine an indeterminate state of an internal node with an external node which use indicated combining
  algorithm.
  
  @param inState
  @param externalNode
  @return