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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def partition_query( self, sql, params=None, param_types=None, partition_size_bytes=None, max_partitions=None, ):
 """Perform a ``ParitionQuery`` API request. :type sql: str :param sql: SQL query statement :type params: dict, {str -> column value} :param params: values for parameter replacement. Keys must match the names used in ``sql``. :type param_types: dict[str -> Union[dict, .types.Type]] :param param_types: (Optional) maps explicit types for one or more param values; required if parameters are passed. :type partition_size_bytes: int :param partition_size_bytes: (Optional) desired size for each partition generated. The service uses this as a hint, the actual partition size may differ. :type max_partitions: int :param max_partitions: (Optional) desired maximum number of partitions generated. The service uses this as a hint, the actual number of partitions may differ. :rtype: iterable of bytes :returns: a sequence of partition tokens :raises ValueError: for single-use snapshots, or if a transaction ID is already associtated with the snapshot. """

        if not self._multi_use:
            raise ValueError("Cannot use single-use snapshot.")

        if self._transaction_id is None:
            raise ValueError("Transaction not started.")

        if params is not None:
            if param_types is None:
                raise ValueError("Specify 'param_types' when passing 'params'.")
            params_pb = Struct(
                fields={key: _make_value_pb(value) for key, value in params.items()}
            )
        else:
            params_pb = None

        database = self._session._database
        api = database.spanner_api
        metadata = _metadata_with_prefix(database.name)
        transaction = self._make_txn_selector()
        partition_options = PartitionOptions(
            partition_size_bytes=partition_size_bytes, max_partitions=max_partitions
        )

        response = api.partition_query(
            session=self._session.name,
            sql=sql,
            transaction=transaction,
            params=params_pb,
            param_types=param_types,
            partition_options=partition_options,
            metadata=metadata,
        )

        return [partition.partition_token for partition in response.partitions]