code: def infer_cardinalities(self, time_series):
      if "feat_static_cat" not in time_series[0]:
          return []
      mat = np.array(
          [elem["feat_static_cat"] for elem in time_series], dtype=int
      )
      return [len(set(xs)) for xs in mat.T]
  
imports: import concurrent.futures
  import logging
  from enum import Enum
  from itertools import chain, starmap
  from typing import Dict, List, Tuple, Union, Optional, Sequence
  import numpy
  from gluonts.core.component import validated
label_desc: Use image node_id 5 for calling the PreprocessOnlyLagFeatures obj's underlying member method code with example usage: obj.infer_cardinalities(time_series) and returns: unknown, list