input: Write a function to crawl a website for a specific type of data and return the extracted data. The function should take a website URL and a specific type of data to crawl as input. If phone numbers are to be crawled, the function should return a list of phone numbers found on the website. If the website URL is 'www.example.com' and the data to crawl is phone numbers, the function should return a list of phone numbers in the format 'XXX-XXX-XXXX'.
  assert crawl_website_for_phone_numbers('www.example.com', 'phone numbers')==['123-456-7890', '987-654-3210']
  assert crawl_website_for_phone_numbers('www.anothersite.com', 'emails')==[]
  assert crawl_website_for_phone_numbers('www.sitewithoutdata.com', 'phone numbers')==[]
  assert crawl_website_for_phone_numbers('www.example.com', 'emails')==[]
  assert crawl_website_for_phone_numbers('www.sitewitherror.com', 'phone numbers')==[]
output: import re
  import requests
  
  def crawl_website_for_phone_numbers(url, data_type):
      if data_type != 'phone numbers':
          return []
      
      try:
          response = requests.get(f'http://{url}')
          response.raise_for_status()
          html_content = response.text
      except:
          return []
      
      phone_numbers = re.findall(r'\b\d{3}-\d{3}-\d{4}\b', html_content)
      return phone_numbers