class_docstr: Wrapper class for interacting with per-group state data in `applyInPandasWithState`.
docstr: Whether state exists or not.
docstr_tok: ["Whether","state","exists","or","not","."]
code: def exists(self) -> bool:
      """
      Whether state exists or not.
      """
      return self._defined
  
imports: import datetime
  import json
  from typing import Tuple, Optional
  from pyspark.sql.types import DateType, Row, StructType
  from pyspark.sql.utils import has_numpy
  from pyspark.errors import PySparkTypeError, PySparkValueError, PySparkRuntimeError
label_desc: Use image node_id 2 for calling the GroupState obj's underlying member method code with example usage: obj.exists() and returns: self