code: def mongo_obs():
      db = mongomock.MongoClient().db
      runs = db.runs
      metrics = db.metrics
      fs = gridfs.GridFS(db)
      return MongoObserver.create_from(
          runs, fs, metrics_collection=metrics
      )
  
imports: import datetime
  import os
  import sys
  from glob import glob
  import mock
  import pytest
  from sacred.metrics_logger import ScalarMetricLogEntry, linearize_metrics
  import gridfs
  from mongomock.gridfs import enable_gridfs_integration
  from .failing_mongo_mock import FailingMongoClient
  from sacred.dependencies import get_digest
  from sacred.observers.mongo import MongoObserver, force_bson_encodeable
label_desc: Use image node_id 4 for calling a global function with example usage: mongo_obs() and returns: MongoObserver