为什么当我想要使用python-selenium从chrome下载文件时会出现错误

from selenium import webdriver
from selenium.webdriver.common.by import By
options = webdriver.ChromeOptions()
preferences = {"download.default_directory": "D:sourcetree_webscraping_exampletesting", "safebrowsing.enabled": "false"}
options.add_experimental_option("prefs", preferences)
driver = webdriver.Chrome(options=options)
driver.get("https://www.whatsapp.com/download/")
driver.find_element(By.XPATH, "//a[text() = 'Download for Windows']").click()

出现错误(无法打开文件"D:\sourcetree_\webscrapeing_example\Unttled-1'：[Erno 2]没有这样的文件或目录(。我可以知道怎么解决吗？