input: Write a function to crawl a given website and extract all phone numbers from its content. The function should return a list of phone numbers found. If no phone numbers are found, an empty list should be returned. The website URL is passed as an argument to the function.
  
  assert crawl_website_for_phone_numbers('www.example.com')==['123-456-7890', '987-654-3210']
  assert crawl_website_for_phone_numbers('www.no_phone_numbers.com')==[]
  assert crawl_website_for_phone_numbers('www.another_example.com')==['555-555-5555']
  assert crawl_website_for_phone_numbers('www.multiple_numbers.com')==['111-111-1111', '222-222-2222', '333-333-3333']
  assert crawl_website_for_phone_numbers('www.invalid_url.com')==[]
  
output: import re
  import requests
  
  def crawl_website_for_phone_numbers(url):
      try:
          response = requests.get(f"http://{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 []