human
Solve the following python programming problem given the following code:
@gen.engine
def GetMergedLogsFileList(merged_store, logs_paths, marker, callback):
assistant
#Here is the Python code you requested.

    """Fetch the list of file names from S3.
    """
    registry_file = logs_paths.ProcessedRegistryPath()
    def _WantFile(filename):
        if (filename == registry_file):
            return False
        instance = logs_paths.MergedLogPathToInstance(filename)
        if (instance is None):
            logging.error(('Could    not    extract    instance    from    file    name    %s' % filename))
            return False
        return ((not options.options.ec2_only) or logs_util.IsEC2Instance(instance))
    base_path = logs_paths.MergedDirectory()
    marker = (os.path.join(base_path, marker) if (marker is not None) else None)
    file_list = (yield gen.Task(store_utils.ListAllKeys, merged_store, prefix=base_path, marker=marker))
    files = [f for f in file_list if _WantFile(f)]
    files.sort()
    logging.info(('found    %d    merged    log    files,    analyzing    %d' % (len(file_list), len(files))))
    callback(files)