def METHOD_NAME(request, usage_key_str, path):
    """
    Serve a static file that got added to the XBlock's export_fs during XBlock
    serialization. Typically these would be video transcript files.
    """
    # Parse the usage key:
    try:
        usage_key = UsageKey.from_string(usage_key_str)
    except (ValueError, InvalidKeyError):
        raise ValidationError('Invalid usage key')  # lint-amnesty, pylint: disable=raise-missing-from
    if usage_key.block_type in ('course', 'chapter', 'sequential'):
        raise ValidationError('Requested XBlock tree is too large - export verticals or their children only')
    course_key = usage_key.context_key
    if not isinstance(course_key, CourseLocator):
        raise ValidationError('Invalid usage key: not a modulestore course')
    # Make sure the user has permission on that course
    if not has_studio_read_access(request.user, course_key):
        raise PermissionDenied("You must be a member of the course team in Studio to export OLX using this API.")
    block = modulestore().get_item(usage_key)
    serialized = serialize_modulestore_block_for_blockstore(block)
    static_file = None
    for f in serialized.static_files:
        if f.name == path:
            static_file = f
            break
    if static_file is None:
        raise NotFound
    response = HttpResponse(static_file.data, content_type='application/octet-stream')
    response['Content-Disposition'] = f'attachment; filename="{path}"'
    return response