我正在嘗試支持以下功能場(chǎng)景：Feature: test  Scenario: Test optional      Given attacked by samurai        And attacked by samurai from behind我的步驟文件是from behave import step@step('attacked by {opponent}')def step_attacked_by(context, opponent):    print(opponent)@step('attacked by {opponent} from {direction}')def step_attacked_by(context, opponent, direction):    print(opponent)    print(direction)我收到錯(cuò)誤：behave.step_registry.AmbiguousStep: @step('attacked by {opponent} from {direction}') has already been defined in  existing step @step('attacked by {opponent}') at steps/test.py:5然后我嘗試使用可選參數(shù)：我的功能文件：Feature: test  Scenario: Test optional      Given attacked by a samurai我的步驟文件：import parsefrom behave import step, register_type@parse.with_pattern(r"a\s+")def parse_word_a(text):    """Type converter for "a " (followed by one/more spaces)."""    return text.strip()register_type(a_=parse_word_a)@step('attacked by {:a_?}{opponent}')def step_attacked_by(context, a_, opponent):    print(a_)    print(opponent)我收到此錯(cuò)誤：    raise ValueError('format spec %r not recognised' % type)ValueError: format spec 'a_?' not recognised我認(rèn)為我真的不需要一個(gè)可選參數(shù)，只要我可以消除第一個(gè)示例中的步驟的歧義即可。