./data/example_6.py:101:16: F821 undefined name 'S3Transfer'
    transfer = S3Transfer(boto3.client('s3', 'us-west-2'))
               ^
./data/example_6.py:101:27: F821 undefined name 'boto3'
    transfer = S3Transfer(boto3.client('s3', 'us-west-2'))
                          ^
./data/example_6.py:114:14: F821 undefined name 'boto3'
    client = boto3.client('s3', 'us-west-2')
             ^
./data/example_6.py:115:14: F821 undefined name 'TransferConfig'
    config = TransferConfig(
             ^
./data/example_6.py:120:16: F821 undefined name 'S3Transfer'
    transfer = S3Transfer(client, config)
               ^
./data/example_6.py:48:14: F821 undefined name 'boto3'
    client = boto3.client('s3', 'us-west-2')
             ^
./data/example_6.py:49:16: F821 undefined name 'S3Transfer'
    transfer = S3Transfer(client)
               ^
./data/example_6.py:84:32: F821 undefined name 'os'
            self._size = float(os.path.getsize(filename))
                               ^
./data/example_6.py:86:26: F821 undefined name 'threading'
            self._lock = threading.Lock()
                         ^
./data/example_6.py:94:17: F821 undefined name 'sys'
                sys.stdout.write(
                ^
./data/example_6.py:98:17: F821 undefined name 'sys'
                sys.stdout.flush()
                ^
