code: def test_context():
      context = Context({"foo": "bar"})
      assert context["foo"] == Value("bar")
  
      context = Context(foo="bar")
      assert context["foo"] == Value("bar")
  
      context["foobar"] = "foobar"
      assert context["foobar"] == Value("foobar")
  
      del context["foobar"]
      assert "foobar" not in context
      assert "foo" in context
  
      with pytest.raises(KeyError):
          _ = context["foobar"]
  
imports: from dataclasses import asdict
  from math import pi
  import pytest
  from dvc.fs import LocalFileSystem
  from dvc.parsing import DEFAULT_PARAMS_FILE
  from dvc.parsing.context import Context, CtxDict, CtxList, KeyNotInContext, MergeError, ParamsLoadError, Value, recurse_not_a_node
  from dvc.utils import relpath
  from dvc.utils.serialize import dumps_yaml
label_desc: Use image node_id 1 for calling a global function with example usage: test_context() without return types