How to use the cython.test_fail_if_path_exists function in Cython

@cython.test_fail_if_path_exists(
    "//MulNode",
    "//PowNode",
)
def binop_mul_pow():
    """
    >>> print_big_ints(binop_mul_pow())
    (800, 12193263111263526900, 248832, 12467572902176589255564000298710470656)
    """
    mul_int = 20 * 40
    mul_large_int = 1234567890 * 9876543210
    pow_int = 12 ** 5
    pow_large_int = 1234 ** 12
    return (mul_int, mul_large_int, pow_int, pow_large_int)

@cython.test_fail_if_path_exists(
    "//UnaryMinusNode",
    "//UnaryPlusNode",
)
def unop_floats():
    """
    >>> unop_floats()
    (False, 2.0, -2.0, False, 2.0, -2.0, -2.0)
    """
    not1   = not 2.0
    plus1  = + 2.0
    minus1 = - 2.0
    not3   = not not not 2.0
    plus3  = +++ 2.0
    minus3 = --- 2.0
    mix    = +-++-- 2.0
    return not1, plus1, minus1, not3, plus3, minus3, mix

@cython.test_fail_if_path_exists("//CFuncDeclaratorNode//IntNode[@value = '-1']")
@cython.test_assert_path_exists("//CFuncDeclaratorNode")
@cython.ccall
@cython.returns(cython.long)
@cython.exceptval(check=True)
def ccall_except_check_always(x):
    """
    >>> ccall_except_check_always(41)
    42
    >>> ccall_except_check_always(0)
    Traceback (most recent call last):
    ValueError
    """
    if x == 0:
        raise ValueError
    return x+1

@cython.test_fail_if_path_exists(
    "//MulNode",
    "//ListNode//IntNode",
)
def zero_mult_list():
    """
    >>> zero_mult_list()
    []
    """
    return 0 * [1, 2] * 0

@cython.test_fail_if_path_exists("//IfStatNode")
@cython.test_assert_path_exists("//PrintStatNode")
def test_yield_in_const_conditional_true():
    """
    >>> list(test_yield_in_const_conditional_true())
    None
    [1]
    """
    if True:
        print((yield 1))

@cython.test_fail_if_path_exists('//AttributeNode')
@cython.test_assert_path_exists('//PythonCapiCallNode')
@cython.locals(d=dict)
def setdefault2(d, key, value):
    """
    >>> d = {}
    >>> setdefault2(d, 1, 2)
    2
    >>> len(d)
    1
    >>> setdefault2(d, 1, 2)
    2
    >>> len(d)
    1
    >>> l = setdefault2(d, 2, [])
    >>> len(d)
    2

@cython.test_fail_if_path_exists(
    '//IntNode[@value = "1"]',
    '//IntNode[@value = "8"]',
    '//PrimaryCmpNode[.//IntNode[@value = "4"] and .//IntNode[@value = "5"]]',
    '//PrimaryCmpNode[.//IntNode[@value = "2"] and .//IntNode[@value = "7"]]',
    '//BoolNode',
)
def cascaded_cmp_with_partial_constants(a, b):
    """
    >>> cascaded_cmp_with_partial_constants(3, 6)
    True
    >>> cascaded_cmp_with_partial_constants(1, 6)
    False
    >>> cascaded_cmp_with_partial_constants(4, 6)
    False
    >>> cascaded_cmp_with_partial_constants(3, 7)
    False

@cython.test_fail_if_path_exists('//SimpleCallNode[@function.type.is_builtin_type = True]')
def call_str(arg):
    """
    >>> print(call_str('TEST'))
    STR
    """
    return str(arg)

@cython.test_fail_if_path_exists(
    "//ComprehensionNode",
    "//ForInStatNode",
)
@cython.test_assert_path_exists(
    "//ListNode",
)
def for_in_empty_nested_listcomp():
    """
    >>> for_in_empty_nested_listcomp()
    []
    """
    return [x for _ in [] for x in [1, 2, 3]]