code: public String format(GeometryIndex index) {
  		if (index.hasChild()) {
  			return "geometry" + index.getValue() + "." + format(index.getChild());
  		}
  		switch (index.getType()) {
  			case TYPE_VERTEX:
  				return "vertex" + index.getValue();
  			case TYPE_EDGE:
  				return "edge" + index.getValue();
  			default:
  				return "geometry" + index.getValue();
  		}
  	}
docs: Format a given geometry index, creating something like "geometry2.vertex1".
  
  @param index
  The geometry index to format.
  @return Returns the string value resulting from the index.