如何使用Selenium抓取iframe内的span标记？

from selenium import webdriver
from selenium.webdriver.common.by import By
from selenium.webdriver.support.ui import WebDriverWait
from selenium.webdriver.support import expected_conditions as EC

driver = webdriver.Chrome("path/to/chromedriver")

driver.get("http://example.com")

iframe = driver.find_element(By.XPATH, "//iframe[@id='iframe_id']")
driver.switch_to.frame(iframe)

span = WebDriverWait(driver, 10).until(EC.presence_of_element_located((By.XPATH, "//span[@class='span_class']")))
span_content = span.text

driver.switch_to.default_content()

driver.quit()