def METHOD_NAME(stdout: str) -> List[str]:
    """
    Grab the list of downloaded files from the output of 'aws s3 cp'. Lines look
    like:
        download: s3://some/prefix/a_file.txt to a_file.txt
    """
    files = []
    for line in stdout.split("\n"):
        line = line.strip()
        if line == "":
            continue
        m = S3_DOWNLOAD_REGEX.match(line)
        if m:
            files.append(m.groups()[0])
    return files