code: def __str__(self) -> str:
      return "%s(%s)" % (
          type(self).__name__,
          ", ".join("%s=%s" % item for item in vars(self).items()),
      )
  
file_path: evadb/evadb/optimizer/group_expression.py
imports: from typing import List
  from evadb.constants import UNDEFINED_GROUP_ID
  from evadb.optimizer.operators import Operator
  from evadb.optimizer.rules.rules_base import RuleType
label_desc: Use image node_id 13 for calling the GroupExpression obj's underlying member method code with example usage: obj.__str__() and returns: unknown