input: Write a python function to extract titles and descriptions from a webpage given its URL using BeautifulSoup.
  assert extract_titles_and_descriptions('http://example.com/page') == [('Title 1', 'Description 1'), ('Title 2', 'Description 2')]
  assert extract_titles_and_descriptions('http://example.com/anotherpage') == [('Another Title 1', 'Another Description 1'), ('Another Title 2', 'Another Description 2')]
output: def extract_titles_and_descriptions(url):
      import requests
      from bs4 import BeautifulSoup
  
      response = requests.get(url)
      soup = BeautifulSoup(response.content, 'html.parser')
  
      titles_and_descriptions = []
  
      for item in soup.find_all('div', class_='item'):
          title = item.find('h2').text
          description = item.find('p').text
          titles_and_descriptions.append((title, description))
  
      return titles_and_descriptions