<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def compose_path(pub, uuid_url=False):
 """ Compose absolute path for given `pub`. Args: pub (obj):
 :class:`.DBPublication` instance. uuid_url (bool, default False):
 Compose URL using UUID. Returns: str: Absolute url-path of the publication, without server's address \ and protocol. Raises: PrivatePublicationError: When the `pub` is private publication. """

    if uuid_url:
        return join(
            "/",
            UUID_DOWNLOAD_KEY,
            str(pub.uuid)
        )

    return join(
        "/",
        DOWNLOAD_KEY,
        basename(pub.file_pointer),
        basename(pub.filename)
    )