code: def execute_task_stack(self, task_stack):
      while not task_stack.empty():
          task = task_stack.pop()
          task.execute()
  
file_path: evadb/test/unit_tests/optimizer/test_cost_model.py
imports: import unittest
  from copy import copy
  from mock import MagicMock
  from evadb.optimizer.group_expression import GroupExpression
  from evadb.optimizer.operators import Operator
  from evadb.optimizer.optimizer_context import OptimizerContext
  from evadb.optimizer.optimizer_tasks import OptimizeGroup
  from evadb.optimizer.plan_generator import PlanGenerator
  from evadb.optimizer.property import PropertyType
label_desc: Use image node_id 1 for calling the CostModel obj's underlying member method code with example usage: obj.execute_task_stack(task_stack) without return types