Return nothing

def visit(self, t1, t2, value, data):
        '''
        Return nothing
        '''
        if self.is_visited(t1, t2):
            return

        k1 = str(t1)
        k2 = str(t2)
        if k1 not in self._history:
            self._history[k1] = {}
        self._history[k1][k2] = True

        if value < self._min_value:
            self._min_value = value
            self._min_value_t1 = t1
            self._min_value_t2 = t2
            self._min_value_data = data