How to use the deal.linter._func.Func.from_astroid function in deal

def test_check_pure_no_returns():
    checker = CheckPure()
    text = """
    @deal.pure
    def test(a):
        a + 3
    """
    text = dedent(text).strip()
    funcs1 = Func.from_ast(ast.parse(text))
    funcs2 = Func.from_astroid(astroid.parse(text))
    for func in (funcs1[0], funcs2[0]):
        actual = [tuple(err) for err in checker(func)]
        assert len(actual) == 1
        expected = 'DEAL023 pure contract error (no return)'
        assert actual[0][2] == expected

def test_check_returns_ok_unresolved():
    checker = CheckReturns()
    text = """
    @deal.post(unknown)
    def test(a):
        return 1
    """
    text = dedent(text).strip()
    funcs1 = Func.from_ast(ast.parse(text))
    funcs2 = Func.from_astroid(astroid.parse(text))
    for func in (funcs1[0], funcs2[0]):
        actual = tuple(checker(func))
        assert not actual

def test_check_returns():
    checker = CheckReturns()
    text = """
    @deal.post(lambda x: x > 0)
    def test(a):
        if a:
            return 1
        else:
            return -1
    """
    text = dedent(text).strip()
    funcs1 = Func.from_ast(ast.parse(text))
    funcs2 = Func.from_astroid(astroid.parse(text))
    for func in (funcs1[0], funcs2[0]):
        actual = [tuple(err) for err in checker(func)]
        expected = [(6, 15, 'DEAL012 post contract error (-1)')]
        assert actual == expected

def test_resolve_func():
    text = """
    import deal

    def contract(x):
        return x > 0

    @deal.post(contract)
    def f(x):
        ...
    """
    text = dedent(text).strip()
    funcs = Func.from_astroid(astroid.parse(text))
    assert len(funcs) == 2
    func = funcs[-1]
    assert len(func.contracts) == 1
    c = func.contracts[0]
    assert c.run(1) is True
    assert c.run(-1) is False

def test_return_message():
    text = """
    import deal

    @deal.post(lambda x: x > 0 or 'oh no!')
    def f(x):
        return x
    """
    text = dedent(text).strip()
    funcs1 = Func.from_ast(ast.parse(text))
    assert len(funcs1) == 1
    funcs2 = Func.from_astroid(astroid.parse(text))
    assert len(funcs2) == 1
    for func in (funcs1[0], funcs2[0]):
        assert len(func.contracts) == 1
        c = func.contracts[0]
        assert c.run(1) is True
        assert c.run(-1) == 'oh no!'

def test_from_astroid():
    funcs = Func.from_astroid(astroid.parse(TEXT))
    assert len(funcs) == 3
    assert len(funcs[0].contracts) == 2

checker = CheckPre()
    text = """
    @deal.pre(lambda x: x > 0)
    def example(x):
        return -x

    @deal.raises()
    def caller():
        return example(-3)

    # ignore funcs without contracts
    def caller():
        return example(-3)
    """
    text = dedent(text).strip()
    funcs = Func.from_astroid(astroid.parse(text))
    assert len(funcs) == 3
    actual = []
    for func in funcs:
        actual.extend(tuple(err) for err in checker(func))
    expected = [(7, 11, 'DEAL011 pre contract error (-3)')]
    assert actual == expected

def test_skip_asserts_in_tests():
    checker = CheckAsserts()
    text = """
    def test_example(a):
        assert False, "oh no!"
    """
    text = dedent(text).strip()
    funcs1 = Func.from_ast(ast.parse(text))
    funcs2 = Func.from_astroid(astroid.parse(text))
    for func in (funcs1[0], funcs2[0]):
        actual = list(checker(func))
        assert actual == []

def test_exceptions():
    funcs1 = Func.from_ast(ast.parse(TEXT))
    assert len(funcs1) == 1
    funcs2 = Func.from_astroid(astroid.parse(TEXT))
    assert len(funcs2) == 1
    for func in (funcs1[0], funcs2[0]):
        assert len(func.contracts) == 1
        contract = func.contracts[0]
        assert contract.exceptions == [ValueError, 'UnknownError']