code: def called_alts_from_genotype(self):
          '''Returns a set of the (maybe REF and) ALT strings that were called, using GT in FORMAT.
          Returns None if GT not in the record'''
          if 'GT' not in self.FORMAT:
              return None
  
          genotype_indexes = set([int(x) for x in self.FORMAT['GT'].split('/')])
          alts = set()
  
          for i in genotype_indexes:
              if i == 0:
                  alts.add(self.REF)
              else:
                  alts.add(self.ALT[i-1])
  
          return altf called_alts_from_genotype(self):
          '''Returns a set of the (maybe REF and) ALT strings that were called, using GT in FORMAT.
          Returns None if GT not in the record'''
          if 'GT' not in self.FORMAT:
              return None
  
          genotype_indexes = set([int(x) for x in self.FORMAT['GT'].split('/')])
          alts = set()
  
          for i in genotype_indexes:
              if i == 0:
                  alts.add(self.REF)
              else:
                  alts.add(self.ALT[i-1])
  
          return alts
docs: Returns a set of the (maybe REF and) ALT strings that were called, using GT in FORMAT.
          Returns None if GT not in the record