code: public Category getLCS(Category category1, Category category2) throws WikiApiException {
          return getLCS(category1.getPageId(),category2.getPageId());
      }
docs: Gets the lowest common subsumer (LCS) of two nodes.
  The LCS of two nodes is first node on the path to the root, that has both nodes as sons.
  Nodes that are not in the same connected component as the root node are defined to have no LCS.
  @param category1 The first category node.
  @param category2 The second category node.
  @return The lowest common subsumer of the two nodes, or null if there is no LCS.