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

def test_check_raises_inherited():
    checker = CheckRaises()
    text = """
    @deal.raises(LookupError)
    def test(a):
        raise KeyError
        raise ValueError
    """
    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 = [(4, 10, 'DEAL021 raises contract error (ValueError)')]
        assert actual == expected

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_with_message():
    checker = CheckReturns()
    text = """
    @deal.post(lambda x: x > 0 or 'oh no!')
    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 oh no! (-1)')]
        assert actual == expected

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']

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_check_asserts():
    checker = CheckAsserts()
    text = """
    def 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 = [tuple(err) for err in checker(func)]
        expected = [(2, 11, 'DEAL031 assert error (False)')]
        assert actual == expected

def test_repr():
    funcs1 = Func.from_ast(ast.parse(TEXT))
    funcs2 = Func.from_astroid(astroid.parse(TEXT))
    for func in (funcs1[0], funcs2[0]):
        assert repr(func) == 'Func(post, raises)'

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 == []