code: def is_homozygous(self):
          '''Returns true iff this variant has a GT field and is homozygous, which here
          means that the genotype is n/n (where n can be any number).'''
          if self.FORMAT is None:
              return False
          else:
              genotypes = set(self.FORMAT.get('GT', '0/1').split('/'))
              return '.' not in genotypes and len(genotypes) == f is_homozygous(self):
          '''Returns true iff this variant has a GT field and is homozygous, which here
          means that the genotype is n/n (where n can be any number).'''
          if self.FORMAT is None:
              return False
          else:
              genotypes = set(self.FORMAT.get('GT', '0/1').split('/'))
              return '.' not in genotypes and len(genotypes) == 1
docs: Returns true iff this variant has a GT field and is homozygous, which here
          means that the genotype is n/n (where n can be any number).