code: def test_stash() -> None:
      stash = Stash()
  
      assert len(stash) == 0
      assert not stash
  
      key1 = StashKey[str]()
      key2 = StashKey[int]()
  
      # Basic functionality - single key.
      assert key1 not in stash
      stash[key1] = "hello"
      assert key1 in stash
      assert stash[key1] == "hello"
      assert stash.get(key1, None) == "hello"
      stash[key1] = "world"
      assert stash[key1] == "world"
      # Has correct type (no mypy error).
      stash[key1] + "string"
      assert len(stash) == 1
      assert stash
  
      # No interaction with another key.
      assert key2 not in stash
      assert stash.get(key2, None) is None
      with pytest.raises(KeyError):
          stash[key2]
      with pytest.raises(KeyError):
          del stash[key2]
      stash[key2] = 1
      assert stash[key2] == 1
      # Has correct type (no mypy error).
      stash[key2] + 20
      del stash[key1]
      with pytest.raises(KeyError):
          del stash[key1]
      with pytest.raises(KeyError):
          stash[key1]
  
      # setdefault
      stash[key1] = "existing"
      assert stash.setdefault(key1, "default") == "existing"
      assert stash[key1] == "existing"
      key_setdefault = StashKey[bytes]()
      assert stash.setdefault(key_setdefault, b"default") == b"default"
      assert stash[key_setdefault] == b"default"
      assert len(stash) == 3
      assert stash
  
      # Can't accidentally add attributes to stash object itself.
      with pytest.raises(AttributeError):
          stash.foo = "nope"  # type: ignore[attr-defined]
  
      # No interaction with another stash.
      stash2 = Stash()
      key3 = StashKey[int]()
      assert key2 not in stash2
      stash2[key2] = 100
      stash2[key3] = 200
      assert stash2[key2] + stash2[key3] == 300
      assert stash[key2] == 1
      assert key3 not in stash
  
imports: import pytest
  from _pytest.stash import Stash
  from _pytest.stash import StashKey
label_desc: Use image node_id 1 for calling a global function with example usage: test_stash() without return types