code: def save_json(self, obj, filename):
      key = gcs_join(self.dir, filename)
      blob = self.bucket.blob(key)
      blob.upload_from_string(
          json.dumps(flatten(obj), sort_keys=True, indent=2),
          content_type="text/json",
      )
  
imports: import json
  import os
  import os.path
  import re
  from typing import Optional
  from sacred.commandline_options import cli_option
  from sacred.dependencies import get_digest
  from sacred.observers.base import RunObserver
  from sacred.serializer import flatten
  from sacred.utils import PathType
label_desc: Use image node_id 10 for calling the GoogleCloudStorageObserver obj's underlying member method code with example usage: obj.save_json(obj, filename) without return types