code: def up(db, dataset_name):
      match_d = {"name": dataset_name}
      dataset_dict = db.datasets.find_one(match_d)
  
      if "annotation_runs" not in dataset_dict:
          dataset_dict["annotation_runs"] = {}
  
      brain_methods = dataset_dict.get("brain_methods", {})
      for run_doc in brain_methods.values():
          config = run_doc.get("config", {})
          config_cls = config.get("cls", "")
          if config_cls == "fiftyone.brain.similarity.SimilarityConfig":
              config["model"] = None
              config["metric"] = "euclidean"
  
      db.datasets.replace_one(match_d, dataset_dict)
  
label_desc: Use image node_id 1 for calling a global function with example usage: up(db, dataset_name) without return types