def is_active(self):
pass<EOL>
Tests if this operable is active.

        ``is_active()`` is ``true`` if ``is_operational()`` is ``true``
        and ``is_disabled()`` is ``false,`` or ``is_enabled()`` is
        ``true``.

        return: (boolean) - ``true`` if this operable is on, ``false``
                if it is off
        *compliance: mandatory -- This method must be implemented.*