code: private Term evalIsBlank(Function term) {
  		Term teval = eval(term.getTerm(0));
  		if (teval instanceof Function) {
  			Function function = (Function) teval;
  			Predicate predicate = function.getFunctionSymbol();
  			return termFactory.getBooleanConstant(predicate instanceof BNodePredicate);
  		}
  		return term;
  	}
docs: /*
  Expression evaluator for isBlank() function