code: def tenses(self, verb, parse=True):
          
          verb = verb.lower()
          a = set()
          b = self.lemma(verb, parse=parse)
          v = []
          if b in self:
              v = self[b]
          elif parse is True: # rule-based
              v = self.find_lexeme(b)
          # For each tense in the verb lexeme that matches the given tense,
          # 1) retrieve the tense tuple,
          # 2) retrieve the tense tuples for which that tense is a default.
          for i, tense in enumerate(v):
              if tense == verb:
                  for id, index in self._format.items():
                      if i == index:
                          a.add(id)
                  for id1, id2 in self._default.items():
                      if id2 in a:
                          a.add(id1)
                  for id1, id2 in self._default.items():
                      if id2 in a:
                          a.add(id1)
          a = (TENSES[id][:-2] for id in a)
          a = Tenses(sorted(a))
          return a
docs: Returns a list of possible tenses for the given inflected verb.