input: Write a python function to fetch the titles and URLs of the trending news stories from the BBC news website.
  assert len(fetch_trending_stories()) > 0
  assert isinstance(fetch_trending_stories()[0], tuple)
  assert all('http' in url for _, url in fetch_trending_stories())
output: def fetch_trending_stories():
      import requests
      from bs4 import BeautifulSoup
  
      url = 'https://www.bbc.com/news'
      response = requests.get(url)
      soup = BeautifulSoup(response.content, 'html.parser')
  
      stories = []
  
      for item in soup.select('.nw-o-link-split__anchor'):
          title = item.get_text()
          link = item['href']
          if not link.startswith('http'):
              link = 'https://www.bbc.com' + link
          stories.append((title, link))
      
      return stories