docs: 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