or the os-release file will be empty.

        * ``distro_release_file`` (string): The path name of the
          `distro release file`_ that is to be used as a data source.

          An empty string (the default) will cause a default search algorithm
          to be used (see `distro release file`_ for details).

          If the specified distro release file does not exist, or if no default
          distro release file can be found, the data source for the distro
          release file will be empty.

        * ``include_uname`` (bool): Controls whether uname command output is
          included as a data source. If the uname command is not available in
          the program execution path the data source for the uname command will
          be empty.

        * ``root_dir`` (string): The absolute path to the root directory to use
          to find distro-related information files. Note that ``include_*``
          parameters must not be enabled in combination with ``root_dir``.

        * ``include_oslevel`` (bool): Controls whether (AIX) oslevel command
          output is included as a data source. If the oslevel command is not
          available in the program execution path the data source will be
          empty.

        Public instance attributes:

        * ``os_release_file`` (string): The path name of the
          `os-release file`_ that is actually used as a data source. The
          empty string if no distro release file is used as a data source.

        * ``distro_release_file`` (string): The path name of the
          `distro release file`_ that is actually used as a data source. The
          empty string if no distro release file is used as a data source.

        * ``include_lsb`` (bool): The result of the ``include_lsb`` parameter.
          This controls whether the lsb information will be loaded.

        * ``include_uname`` (bool): The result of the ``include_uname``
          parameter. This controls whether the uname information will
          be loaded.

        * ``include_oslevel`` (bool): The result of the ``include_oslevel``
          parameter. This controls whether (AIX) oslevel information will be
          loaded.

        * ``root_dir`` (string): The result of the ``root_dir`` parameter.
          The absolute path to the root directory to use to find distro-related
          information files.

        Raises:

        * :py:exc:`ValueError`: Initialization parameters combination is not
           supported.

        * :py:exc:`OSError`: Some I/O issue with an os-release file or distro
          release file.

        * :py:exc:`UnicodeError`: A data source has unexpected characters or
          uses an unexpected encoding.
        