code: def test_os_path4(self):
      self.run_test(
          'def os_path4(l): import os; return os.path.join("lili/", l)',
          "mypath",
          os_path4=[str],
      )
  
file_path: pythran/pythran/tests/test_os.py
imports: from pythran.tests import TestEnv
label_desc: Use image node_id 4 for calling the TestOs obj's underlying member method code with example usage: obj.test_os_path4() without return types