code: def samples_by_indices_nomapping(self, indices):
          
          if not self._random_access:
              raise TypeError('samples_by_indices_nomapping method not '
                              'supported as one or more of the underlying '
                              'data sources does not support random access')
          batch = self.source.samples_by_indices_nomapping(indices)
          return self.fn(*batch)
docs: Gather a batch of samples by indices *without* applying any index
          mapping.
  
          Parameters
          ----------
          indices: 1D-array of ints or slice
              An index array or a slice that selects the samples to retrieve
  
          Returns
          -------
          nested list of arrays
              A mini-batch