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.
docstr: Process the DataNode that is an input to an operator call. Detect if the DataNode was
  produced on the same nesting level. If not, split accordingly to the stack of the previous
  conditions. Caches the previously processed DataNodes to not do repeated splitting.
docstr_tok: ["Process","the","DataNode","that","is","an","input","to","an","operator","call",".","Detect","if","the","DataNode","was","produced","on","the","same","nesting","level",".","If","not",",","split","accordingly","to","the","stack","of","the","previous","conditions",".","Caches","the","previously","processed","DataNodes","to","not","do","repeated","splitting","."]
code: def preprocess_input(self, data_node):
      """Process the DataNode that is an input to an operator call. Detect if the DataNode was
      produced on the same nesting level. If not, split accordingly to the stack of the previous
      conditions. Caches the previously processed DataNodes to not do repeated splitting.
      """
      stack_level = self._find_closest(data_node)
      logging.log(
          8,
          (
              f"{self._indent()}[IF/Input] {data_node} accessed at level"
              f" {self.stack_depth() - 1} found at {stack_level}."
          ),
      )
      # We already have it cached or produced in this scope.
      if stack_level == self.stack_depth() - 1:
          return self.top().get(data_node)
      # otherwise, we need to fill in the splits.
      return self._realize_split(data_node, stack_level)
  
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 8 for calling the _ConditionStack obj's underlying member method code with example usage: obj.preprocess_input(data_node) and returns: self, self