code: private RelType convertContext(String type)
  	{
  		if (type.equals("I")) return RelType.INPUT;
  		if (type.equals("O")) return RelType.OUTPUT;
  		if (type.equals("B")) return null;
  		throw new IllegalArgumentException("Unknown context: " + type);
  	}
docs: Converts text context to enum.
  @param type context
  @return enum value