class_docstr: Tracks the current if/else scope with the path that we took. Captures the used and produced
  data nodes, applying the necessary splits based on the scope level where they were produced
  and where they are used.
code: def __init__(self):
      self._stack = [_StackEntry(None)]
      self._is_registration_allowed = True
  
imports: from nvidia.dali import _autograph
  from nvidia.dali.data_node import DataNode
  from nvidia.dali import fn
  from nvidia.dali._autograph.utils import ag_logging
  from nvidia.dali._autograph.operators import variables
  from contextlib import contextmanager
  from enum import Enum
  import tree
label_desc: Use image node_id 1 to create a new _ConditionStack object  with example: obj = _ConditionStack()