code: def test_home():
      os.environ.pop("PYG_HOME", None)
      home_dir = osp.expanduser(DEFAULT_CACHE_DIR)
      assert get_home_dir() == home_dir
  
      home_dir = "/tmp/test_pyg1"
      os.environ["PYG_HOME"] = home_dir
      assert get_home_dir() == home_dir
  
      home_dir = "/tmp/test_pyg2"
      set_home_dir(home_dir)
      assert get_home_dir() == home_dir
  
imports: import os
  import os.path
  from torch_geometric import get_home_dir, set_home_dir
  from torch_geometric.home import DEFAULT_CACHE_DIR
label_desc: Use image node_id 1 for calling a global function with example usage: test_home() without return types