input: def web_scraper(url: str) -> List[str]:
      """Create a web scraper that extracts all URLs from a given website using the Python package BeautifulSoup.
      The function should parse the webpage and find all 'a' tags with href attributes, returning the URLs as a list of strings.
  
      >>> web_scraper("http://example.com")
      ['http://example.com/page1', 'http://example.com/page2', 'http://example.com/page3']
      """
output:     from bs4 import BeautifulSoup
      import requests
  
      response = requests.get(url)
      soup = BeautifulSoup(response.text, 'html.parser')
      urls = [a['href'] for a in soup.find_all('a', href=True)]
      return urls