code: def validate(self, class_, tag, contents):
          
  
          super(CertificateChoices, self).validate(class_, tag, contents)
          if self._choice == 2:
              if AttCertVersion.load(Sequence.load(contents)[0].dump()).native == 'v2':
                  self._choice = 3
docs: Ensures that the class and tag specified exist as an alternative. This
          custom version fixes parsing broken encodings there a V2 attribute
          # certificate is encoded as a V1
  
          :param class_:
              The integer class_ from the encoded value header
  
          :param tag:
              The integer tag from the encoded value header
  
          :param contents:
              A byte string of the contents of the value - used when the object
              is explicitly tagged
  
          :raises:
              ValueError - when value is not a valid alternative