input: 
  def extract_urls(url: str) -> List[str]:
      """ Utilizes BeautifulSoup to extract all URLs from a given webpage.
      The function should retrieve the webpage, parse it using BeautifulSoup, 
      and extract all 'href' attributes from 'a' tags. Finally, it returns 
      these URLs as a list.
      >>> extract_urls("https://example.com")
      ['https://example.com/page1', 'https://example.com/page2']
      """
  
output:     import requests
      from bs4 import BeautifulSoup
  
      response = requests.get(url)
      soup = BeautifulSoup(response.text, 'html.parser')
      urls = [a['href'] for a in soup.find_all('a', href=True)]
      return urls