input: Write a python function to extract and return headlines from a given URL using BeautifulSoup.
  assert extract_headlines('https://www.bbc.co.uk/news/business/') != []
  assert isinstance(extract_headlines('https://www.bbc.co.uk/news/business/'), list)
  assert all(isinstance(headline, str) for headline in extract_headlines('https://www.bbc.co.uk/news/business/'))
output: def extract_headlines(url):
      import requests
      from bs4 import BeautifulSoup
  
      response = requests.get(url)
      soup = BeautifulSoup(response.content, 'html.parser')
      
      headlines = []
      for item in soup.find_all('h3'):
          headlines.append(item.get_text())
  
      return headlines