def getid(self, ref):
        """Obtain the reference number of the vgroup following the
        vgroup with the given reference number .

        Args::

          ref    reference number of the vgroup after which to search;
                 set to -1 to start the search at the start of
                 the HDF file

        Returns::

          reference number of the vgroup past the one identified by 'ref'

        An exception is raised if the end of the vgroup is reached.

        C library equivalent : Vgetid
                                                    """

        num = _C.Vgetid(self._hdf_inst._id, ref)
        _checkErr('getid', num, "bad arguments or last vgroup reached")
        return num
Obtain the reference number of the vgroup following the
        vgroup with the given reference number .

        Args::

          ref    reference number of the vgroup after which to search;
                 set to -1 to start the search at the start of
                 the HDF file

        Returns::

          reference number of the vgroup past the one identified by 'ref'

        An exception is raised if the end of the vgroup is reached.

        C library equivalent : Vgetid