code: int getObjectID(Object element) {
          if (element == null) return NULL;
          else if (Cell.class.isInstance(element)) return CELL;
          else if (Table.class.isInstance(element)) return TABLE; 
          return -1;
      }
docs: Returns the type-id of an Object.
  
  @param       element the object of which you'd like to know the type-id, -1 if invalid
  @return the type-id of an object