g): 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.
