code: private int otherIndex(int i) {
          IDoubleBondStereochemistry element = (IDoubleBondStereochemistry) queryElements[i];
          return queryMap.get(element.getStereoBond().getOther(query.getAtom(i)));
      }
docs: Given an index of an atom in the query get the index of the other atom in
  the double bond.
  
  @param i query atom index
  @return the other atom index involved in a double bond