code: private static void checkPolymerIDSConnection(ConnectionNotation not, List<String> listPolymerIDs)
  			throws PolymerIDsException {
  		/* the polymer ids have to be there */
  		checkExistenceOfPolymerID(not.getSourceId().getId(), listPolymerIDs);
  		checkExistenceOfPolymerID(not.getTargetId().getId(), listPolymerIDs);
  	}
docs: method to check for one connection if the two polymer ids exist
  
  @param not
  ConnectionNotation
  @param listPolymerIDs
  List of polymer ids
  @throws PolymerIDsException
  if the polymer ids do not exist