Get a set() of files from a jottapath (a folder)

def filelist(jottapath, JFS):
    """Get a set() of files from a jottapath (a folder)"""
    log.debug("filelist %r", jottapath)
    try:
        jf = JFS.getObject(jottapath)
    except JFSNotFoundError:
        return set() # folder does not exist, so pretend it is an empty folder
    if not isinstance(jf, JFSFolder):
        return False
    return set([f.name for f in jf.files() if not f.is_deleted()])