code: def save_json(self, obj, filename):
      key = s3_join(self.dir, filename)
      self.put_data(
          key, json.dumps(flatten(obj), sort_keys=True, indent=2)
      )
  
imports: import json
  import os
  import os.path
  from sacred.commandline_options import cli_option
  from sacred.dependencies import get_digest
  from sacred.observers.base import RunObserver
  from sacred.serializer import flatten
  import re
  import socket
label_desc: Use image node_id 12 for calling the S3Observer obj's underlying member method code with example usage: obj.save_json(obj, filename) without return types