input: Write a function to crawl a website for phone numbers and return a list of phone numbers in the format XXX-XXX-XXXX. If no phone numbers are found, return an empty list.
  assert crawl_website_for_phone_numbers('www.example.com')==['123-456-7890', '987-654-3210']
  assert crawl_website_for_phone_numbers('www.no_numbers.com')==[]
  assert crawl_website_for_phone_numbers('www.invalid_url.com')==[]
output: def crawl_website_for_phone_numbers(url):
      import re
      import requests
      try:
          response = requests.get(url)
          response.raise_for_status()
          content = response.text
          phone_numbers = re.findall(r'\b\d{3}-\d{3}-\d{4}\b', content)
          return phone_numbers
      except:
          return []