class_docstr: Maintain context information for the optimizer
  
  Arguments:
      _task_queue(OptimizerTaskStack):
          stack to keep track outstanding tasks
class_docstr_tok: ["Maintain","context","information","for","the","optimizer","Arguments",":","_task_queue","(","OptimizerTaskStack",")",":","stack","to","keep","track","outstanding","tasks"]
code: def task_stack(self):
      return self._task_stack
  
file_path: evadb/evadb/optimizer/optimizer_context.py
imports: import copy
  from evadb.constants import UNDEFINED_GROUP_ID
  from evadb.database import EvaDBDatabase
  from evadb.optimizer.cost_model import CostModel
  from evadb.optimizer.group_expression import GroupExpression
  from evadb.optimizer.memo import Memo
  from evadb.optimizer.operators import Dummy, Operator
  from evadb.optimizer.optimizer_task_stack import OptimizerTaskStack
  from evadb.optimizer.rules.rules_manager import RulesManager
label_desc: Use image node_id 5 for calling the OptimizerContext obj's underlying member method code with example usage: obj.task_stack() and returns: self