code: def reftoindex(self, sds_ref):
          
  
          sds_idx = _C.SDreftoindex(self._id, sds_ref)
          _checkErr('reftoindex', sds_idx, 'illegal SDS ref number')
          return sds_idx
docs: Returns the index number of a dataset given the dataset
          reference number.
  
          Args::
  
            sds_ref : dataset reference number
  
          Returns::
  
            dataset index number
  
          C library equivalent : SDreftoindex