code: def client(app):
      return app.test_client()
  
file_path: cornac/tests/cornac/serving/test_app.py
imports: import os
  import pytest
  from cornac.data import Reader, Dataset
  from cornac.models import BPR
label_desc: Use image node_id 3 for calling a global function with example usage: client(app) and returns: app