def visit(self, function, combinator):
        if self.consequent:
            return combinator([function(self.first), function(self.second), function(self.consequent)])
        else:
            return combinator([function(self.first), function(self.second)])
:see: Expression.visit()
dataset/ETHPy150Open nltk/nltk/nltk/sem/drt.py/DrtConcatenation.visit