docs: protected final Segment getSegment( NodeCache cache,
                                          CachedNode parent ) {
          if (parent != null) {
              ChildReference ref = parent.getChildReferences(cache).getChild(key);
              if (ref == null) {
                  // This node doesn't exist in the parent
                  throw new NodeNotFoundInParentException(key, parent.getKey());
              }
              return ref.getSegment();
          }
          // This is the root node ...
          return workspace(cache).childReferenceForRoot().getSegment();
      }