code: public int indexOfRelativeIndex(int relativeIndex) {
      for (int i = 0; i < relativeIndices.length; i++) {
        if (relativeIndices[i] == relativeIndex) {
          return i;
        }
      }
      return -1;
    }
docs: For a particular relative index, returns which element in
  the Clique it is.  For instance, if you created a Clique
  c with relativeIndices [-2, -1, 0], then c.indexOfRelativeIndex(-1)
  will return 1.  If the relative index is not present, it
  will return -1.