code: def _get_queue_types(fed_arrays, data_sources):
      
      try:
          return [data_sources[n].dtype for n in fed_arrays]
      except KeyError as e:
          raise ValueError("Array '{k}' has no data source!"
              .format(k=e.message)), None, sys.exc_info()[2]
docs: Given a list of arrays to feed in fed_arrays, return
      a list of associated queue types, obtained from tuples
      in the data_sources dictionary