How to use the s3transfer.utils.CallArgs function in s3transfer

def setUp(self):
        self.subscriber = RecordingSubscriber()
        self.second_subscriber = RecordingSubscriber()
        self.call_args = CallArgs(subscribers=[
            self.subscriber, self.second_subscriber]
        )
        self.transfer_meta = TransferMeta(self.call_args)
        self.transfer_future = TransferFuture(self.transfer_meta)

def get_call_args(self, **kwargs):
        default_call_args = {
            'fileobj': self.filename, 'bucket': self.bucket,
            'key': self.key, 'extra_args': self.extra_args,
            'subscribers': self.subscribers
        }
        default_call_args.update(kwargs)
        return CallArgs(**default_call_args)

def get_call_args(self, **kwargs):
        default_call_args = {
            'fileobj': self.filename, 'bucket': self.bucket,
            'key': self.key, 'extra_args': self.extra_args,
            'subscribers': self.subscribers
        }
        default_call_args.update(kwargs)
        return CallArgs(**default_call_args)

def setUp(self):
        super(TestDownloadSeekableOutputManager, self).setUp()
        self.download_output_manager = DownloadSeekableOutputManager(
            self.osutil, self.transfer_coordinator,
            io_executor=self.io_executor)

        # Create a fileobj to write to
        self.fileobj = open(self.filename, 'wb')

        self.call_args = CallArgs(fileobj=self.fileobj)
        self.future = self.get_transfer_future(self.call_args)

client operation

        :type subscribers: list(s3transfer.subscribers.BaseSubscriber)
        :param subscribers: The list of subscribers to be invoked in the
            order provided based on the event emit during the process of
            the transfer request.

        :rtype: s3transfer.futures.TransferFuture
        :returns: Transfer future representing the download
        """
        if extra_args is None:
            extra_args = {}
        if subscribers is None:
            subscribers = []
        self._validate_all_known_args(extra_args, self.ALLOWED_DOWNLOAD_ARGS)
        call_args = CallArgs(
            bucket=bucket, key=key, fileobj=fileobj, extra_args=extra_args,
            subscribers=subscribers
        )
        extra_main_kwargs = {'io_executor': self._io_executor}
        if self._bandwidth_limiter:
            extra_main_kwargs['bandwidth_limiter'] = self._bandwidth_limiter
        return self._submit_transfer(
            call_args, DownloadSubmissionTask, extra_main_kwargs)

client operation

        :type subscribers: list(s3transfer.subscribers.BaseSubscriber)
        :param subscribers: The list of subscribers to be invoked in the
            order provided based on the event emit during the process of
            the transfer request.

        :rtype: s3transfer.futures.TransferFuture
        :returns: Transfer future representing the upload
        """
        if extra_args is None:
            extra_args = {}
        if subscribers is None:
            subscribers = []
        self._validate_all_known_args(extra_args, self.ALLOWED_UPLOAD_ARGS)
        call_args = CallArgs(
            fileobj=fileobj, bucket=bucket, key=key, extra_args=extra_args,
            subscribers=subscribers
        )
        extra_main_kwargs = {}
        if self._bandwidth_limiter:
            extra_main_kwargs['bandwidth_limiter'] = self._bandwidth_limiter
        return self._submit_transfer(
            call_args, UploadSubmissionTask, extra_main_kwargs)

may happen at the source object. For example, this client is
            used for the head_object that determines the size of the copy.
            If no client is provided, the transfer manager's client is used
            as the client for the source object.

        :rtype: s3transfer.futures.TransferFuture
        :returns: Transfer future representing the copy
        """
        if extra_args is None:
            extra_args = {}
        if subscribers is None:
            subscribers = []
        if source_client is None:
            source_client = self._client
        self._validate_all_known_args(extra_args, self.ALLOWED_COPY_ARGS)
        call_args = CallArgs(
            copy_source=copy_source, bucket=bucket, key=key,
            extra_args=extra_args, subscribers=subscribers,
            source_client=source_client
        )
        return self._submit_transfer(call_args, CopySubmissionTask)