input: Write a python function to crawl titles from URLs using BeautifulSoup and requests.
  assert crawl_titles('http://example.com')==['Example Domain']
  assert crawl_titles('http://anotherexample.com')==['Another Example Domain']
  assert crawl_titles('http://yetanotherexample.com')==['Yet Another Example Domain']
output: def crawl_titles(url):
      import requests
      from bs4 import BeautifulSoup
  
      response = requests.get(url)
      soup = BeautifulSoup(response.content, 'html.parser')
      titles = [title.get_text() for title in soup.find_all('title')]
      return titles