code: def pytest_sessionstart(session):
      test_root = yatest.common.source_path(
          "catboost/python-package/ut/large/"
      )
  
      python_envs_dir = os.path.join(test_root, "py_envs")
  
      python_envs_lock = FileLock(
          os.path.join(test_root, "py_envs.lock")
      )
      with python_envs_lock:
          if os.path.exists(python_envs_dir):
              return
  
          os.mkdir(python_envs_dir)
          for py_ver in ["3.6"]:
              dst_path = os.path.join(python_envs_dir, py_ver)
  
              whl_dir = yatest.common.source_path(
                  "catboost/python-package"
              )
  
              mk_wheel_env = os.environ.copy()
              mk_wheel_env_keys = list(mk_wheel_env.keys())
              for key in mk_wheel_env_keys:
                  if key.startswith("YA"):
                      del mk_wheel_env[key]
  
              yatest.common.execute(
                  [
                      yatest.common.python_path(),
                      "mk_wheel.py",
                      "-DUSE_SYSTEM_PYTHON=" + py_ver,
                      "-DCATBOOST_OPENSOURCE=yes",
                      "-DCFLAGS=-DCATBOOST_OPENSOURCE=yes",
                      "--host-platform-flag",
                      "CATBOOST_OPENSOURCE=yes",
                      "--host-platform-flag",
                      "CFLAGS=-DCATBOOST_OPENSOURCE=yes",
                      "--build-widget=no",
                  ],
                  cwd=whl_dir,
                  env=mk_wheel_env,
              )
  
              whl_file = None
              for f in os.listdir(whl_dir):
                  if (
                      f.endswith(".whl")
                      and "cp" + py_ver.replace(".", "") in f
                  ):
                      whl_file = os.path.join(whl_dir, f)
                      break
  
              unpack_deps(dst_path, py_ver)
  
              with zipfile.ZipFile(whl_file, "r") as f:
                  f.extractall(os.path.join(dst_path, "catboost"))
  
              unpack_python(dst_path, py_ver)
  
file_path: catboost/catboost/python-package/ut/large/conftest.py
imports: import os
  import tarfile
  import zipfile
  import shutil
  from filelock import FileLock
  import yatest.common
label_desc: Use image node_id 3 for calling a global function with example usage: pytest_sessionstart(session) without return types