请告诉我，我做错了什么？我尝试拖放Selenium，但是每次遇到错误“ AttributeError：move_to需要WebElement”时，

这是我的代码：

from selenium import webdriver
from selenium.webdriver.common.action_chains import ActionChains

chromedriver = '/usr/local/bin/chromedriver'

driver = webdriver.Chrome(chromedriver)
driver.get('http://www.dhtmlgoodies.com/scripts/drag-drop-custom/demo-drag-drop-3.html')

source = driver.find_elements_by_xpath('//*[@id="box3"]')
target = driver.find_elements_by_xpath('//*[@id="box103"]')

action = ActionChains(driver)
action.drag_and_drop(source, target).perform()

我也尝试过，像这样：

from selenium import webdriver
from selenium.webdriver.common.action_chains import ActionChains

chromedriver = '/usr/local/bin/chromedriver'

driver = webdriver.Chrome(chromedriver)
driver.get('http://www.dhtmlgoodies.com/scripts/drag-drop-custom/demo-drag-drop-3.html')

source = driver.find_elements_by_xpath('//*[@id="box3"]')
target = driver.find_elements_by_xpath('//*[@id="box103"]')
ActionChains(driver).click_and_hold(source).move_to_element(target).release(target).perform()

总是出现“ AttributeError：move_to需要WebElement”

Traceback (most recent call last):
  File "drag_and_drop_test.py", line 13, in <module>
    ActionChains(driver).click_and_hold(source).move_to_element(target).release(target).perform()
  File "/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/site-packages/selenium/webdriver/common/action_chains.py", line 121, in click_and_hold
    self.move_to_element(on_element)
  File "/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/site-packages/selenium/webdriver/common/action_chains.py", line 273, in move_to_element
    self.w3c_actions.pointer_action.move_to(to_element)
  File "/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/site-packages/selenium/webdriver/common/actions/pointer_actions.py", line 42, in move_to
    raise AttributeError("move_to requires a WebElement")
AttributeError: move_to requires a WebElement