"from behave import *" 不允许我使用 given when then 等来定义步骤

"from behave import *" is not allowing me to use given when then etc to define steps

from behave import *
import time

DEFAULT_EMAIL = ""
DEFAULT_PASSWORD = ""

@given("unauthenticated user loads the home page")
def step_impl(context):
    assert context.is_sign_in_submit_displayed()

@step("sign-in button is clicked")
def step_impl(context):
    context.login_page = context.login.click_sign_in_submit()

@when("login form is populated with valid credentials")
def step_impl(context):
    context.enter_email(DEFAULT_EMAIL)
    context.enter_password(DEFAULT_PASSWORD)

@then("login is successful")
def step_impl(context):
    assert context.home_page.is_rewards_displayed()
    assert context.home_page.is_account_displayed()

行为导入是否未定义给定时间等?到目前为止,我仅从此片段中看到以下错误:

{
Undefined variable 'given'
Undefined variable 'step'
Undefined variable 'when'
Undefined variable 'then'
}

通过使用 pip3 而不是 pip 安装解决了这个问题。