not have a codename, an empty string is returned.

    Note that the returned codename is not always really a codename. For
    example, openSUSE returns "x86_64". This function does not handle such
    cases in any special way and just returns the string it finds, if any.

    **Lookup hierarchy:**

    * the codename within the "VERSION" attribute of the os-release file, if
      provided,

    * the value of the "Codename" attribute returned by the lsb_release
      command,

    * the value of the "<codename>" field of the distro release file.
    )