How to use the hunter.CallPrinter function in hunter

def test_predicate_q_deduplicate_callprinter():
    out = repr(Q(CallPrinter(), action=CallPrinter()))
    assert out.startswith('CallPrinter(')

        @classmethod
        def local_cm(cls, _):
            pass

        def local_m(self, _):
            pass

        local_dm = Desc(lf)
        local_ddm = Desc(dlf)
        global_dm = Desc(gf)
        global_ddm = Desc(dgf)

    buff = StringIO()
    with trace(actions=[
        hunter.CallPrinter(stream=buff),
        lambda event: buff.write(
            "{0.function}({1})|{2}|{0.kind}\n".format(
                event,
                event.locals.get('_'),
                getattr(event.function_object, '__name__', 'missing')))
    ]):
        gf(1)
        dgf(2)
        lf(3)
        dlf(4)
        Old.old_sm(5)
        Old.old_cm(6)
        Old().old_sm(7)
        Old().old_cm(8)
        Old().old_m(9)
        New.new_sm(10)

def test_callprinter_indent(LineMatcher):
    from sample6 import bar
    out = StringIO()
    with trace(action=CallPrinter(stream=out)):
        bar()

    lm = LineMatcher(out.getvalue().splitlines())
    lm.fnmatch_lines([
        "*sample6.py:1     call      => bar()",
        "*sample6.py:2     line         foo()",
        "*sample6.py:5     call         => foo()",
        "*sample6.py:6     line            try:",
        "*sample6.py:7     line            asdf()",
        "*sample6.py:16    call            => asdf()",
        "*sample6.py:17    line               raise Exception()",
        "*sample6.py:17    exception        ! asdf: (<*Exception'>, Exception(), )",
        "*sample6.py:17    return          <= asdf: None",
        "*sample6.py:7     exception     ! foo: (<*Exception'>, Exception(), )",
        "*sample6.py:8     line            except:",
        "*sample6.py:9     line            pass",

def test_callprinter(LineMatcher):
    out = StringIO()
    with trace(action=CallPrinter(stream=out)):
        foo = bar = lambda x: x

        @foo
        @bar
        def foo():
            return 1

        foo()

    lm = LineMatcher(out.getvalue().splitlines())
    lm.fnmatch_lines([
        '* call      => (x=)',
        '* line         foo = bar = lambda x: x',
        '* return    <= : ',
        '* call      => (x=)',
        '* line         foo = bar = lambda x: x',

def test_clear_env_var(monkeypatch):
    monkeypatch.setitem(os.environ, 'PYTHONHUNTER', '123')
    assert os.environ.get('PYTHONHUNTER') == '123'

    out = StringIO()
    with trace(action=CallPrinter(stream=out), clear_env_var=True):
        assert 'PYTHONHUNTER' not in os.environ

    assert os.environ.get('PYTHONHUNTER') == None