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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def ref(self):
 """Get the reference number of the dataset. Args:: no argument Returns:: dataset reference number C library equivalent : SDidtoref """


        sds_ref = _C.SDidtoref(self._id)
        _checkErr('idtoref', sds_ref, 'illegal SDS identifier')
        return sds_ref