e, the codename in parenthesis is appended, if the
    codename is non-empty (e.g. "7.0 (Maipo)").

    Some distributions provide version numbers with different precisions in
    the different sources of distribution information. Examining the different
    sources in a fixed priority order does not always yield the most precise
    version (e.g. for Debian 8.2, or CentOS 7.1).

    The *best* parameter can be used to control the approach for the returned
    version:

    If *best* is false, the first non-empty version number in priority order of
    the examined sources is returned.

    If *best* is true, the most precise version number out of all examined
    sources is returned.

    **Lookup hierarchy:**

    In all cases, the version number is obtained from the following sources.
    If *best* is false, this order represents the priority order:

    * the value of the "VERSION_ID" attribute of the os-release file,
    * the value of the "Release" attribute returned by the lsb_release
      command,
    * the version number parsed from the "<version_id>" field of the first line
      of the distro release file,
    * the version number parsed from the "PRETTY_NAME" attribute of the
      os-release file, if it follows the format of the distro release files.
    * the version number parsed from the "Description" attribute returned by
      the lsb_release command, if it follows the format of the distro release
      files.
    )