How to use the tink.proto.tink_pb2.Keyset function in tink

def write(self, keyset: tink_pb2.Keyset) -> None:
    if not isinstance(keyset, tink_pb2.Keyset):
      raise tink_error.TinkError('invalid keyset.')
    self._io_stream.write(keyset.SerializeToString())
    self._io_stream.flush()

def read(self) -> tink_pb2.Keyset:
    try:
      return json_format.Parse(self._serialized_keyset, tink_pb2.Keyset())
    except json_format.ParseError as e:
      raise tink_error.TinkError(e)

def public_keyset_handle(self) -> 'KeysetHandle':
    """Returns a new KeysetHandle for the corresponding public keys."""
    public_keyset = tink_pb2.Keyset()
    for key in self._keyset.key:
      public_key = public_keyset.key.add()
      public_key.CopyFrom(key)
      public_key.key_data.CopyFrom(
          registry.Registry.public_key_data(key.key_data))
      _validate_key(public_key)
    public_keyset.primary_key_id = self._keyset.primary_key_id
    return self._create(public_keyset)

def generate_new(cls, key_template: tink_pb2.KeyTemplate) -> 'KeysetHandle':
    """Return a new KeysetHandle.

    It contains a single fresh key generated according to key_template.

    Args:
      key_template: A tink_pb2.KeyTemplate object.

    Returns:
      A new KeysetHandle.
    """
    keyset = tink_pb2.Keyset()
    key_data = registry.Registry.new_key_data(key_template)
    key_id = _generate_unused_key_id(keyset)
    key = keyset.key.add()
    key.key_data.CopyFrom(key_data)
    key.status = tink_pb2.ENABLED
    key.key_id = key_id
    key.output_prefix_type = key_template.output_prefix_type
    keyset.primary_key_id = key_id
    return cls._create(keyset)

def read(self) -> tink_pb2.Keyset:
    if not self._serialized_keyset:
      raise tink_error.TinkError('No keyset found')
    try:
      keyset = tink_pb2.Keyset()
      keyset.ParseFromString(self._serialized_keyset)
      return keyset
    except message.DecodeError as e:
      raise tink_error.TinkError(e)