code: def get_fields(self):
      return {"partition_key"}
  
file_path: petastorm/petastorm/tests/test_end_to_end_predicates_impl.py
imports: from petastorm.predicates import PredicateBase
label_desc: Use image node_id 2 for calling the PartitionKeyInSetPredicate obj's underlying member method code with example usage: obj.get_fields() and returns: unknown