code: def iter_stage_deps(stage, dvc_config):
      """Returns an iteration of dep, parent_stage tuples for a stage.
  
      If a dependency doesn't have a parent (i.e. it relies on a local
      file) the parent stage in the tuple is None.
      """
      out_stages_lookup = None  # lazy init of stages lookup
      stage_config = _stage_config(stage, dvc_config)
      for dep in _stage_deps(stage_config):
          out_stages_lookup = _ensure_out_stages_lookup(
              out_stages_lookup, dvc_config
          )
          yield dep, out_stages_lookup.get(dep)
  
imports: import json
  import logging
  import os
  import subprocess
  import yaml
  from guild import util
  from guild import var
label_desc: Use image node_id 3 for calling a global function with example usage: iter_stage_deps(stage, dvc_config) without return types