code: def prep_data(data, features, session_id, prediction_window, predictions_in_chunk, target=None, verbose=True):
      
      if target is None:
          target = ""
      if verbose:
          result_dict = _extensions._activity_classifier_prepare_data_verbose(
              data, features, session_id, prediction_window, predictions_in_chunk, target)
      else:
          result_dict = _extensions._activity_classifier_prepare_data(
              data, features, session_id, prediction_window, predictions_in_chunk, target)
  
  
      return result_dict["converted_data"] , result_dict["num_of_sessions"]
docs: Convert SFrame to batch form, where each row contains a sequence of length
      predictions_in_chunk * prediction_window, and there is a single label per
      prediction window.