input: Write a python function to extract headlines from a given URL using BeautifulSoup.
  assert extract_headlines("https://www.bbc.com/news/uk-england-london-53741405") == ["Headline1", "Headline2"]
  assert extract_headlines("https://www.bbc.com/news/world-us-canada-53945549") == ["AnotherHeadline1", "AnotherHeadline2"]
  assert extract_headlines("https://www.bbc.com/news/technology-54013640") == ["TechHeadline1", "TechHeadline2"]
output: def extract_headlines(url):
      import requests
      from bs4 import BeautifulSoup
  
      response = requests.get(url)
      soup = BeautifulSoup(response.text, 'html.parser')
      
      # As the HTML structure of news sites can vary, let's assume headlines are in <h3> tags for BBC
      headlines = [h3.get_text() for h3 in soup.find_all('h3')]
      
      return headlines