code: def children(self):
      return self._children
  
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 5 for calling the GroupExpression obj's underlying member method code with example usage: obj.children() and returns: self