input: from typing import List
  
  def extract_urls(webpage_urls: List[str]) -> List[str]:
      """
      This function takes a list of webpage URLs as input and extracts all the URLs listed under the 'a' tags from each webpage.
      It uses the BeautifulSoup Python package to parse the webpages and retrieve the required data.
      
      >>> extract_urls(['http://example.com'])
      ['http://example2.com', '/internal', '#fragment']
      """
output:     from bs4 import BeautifulSoup
      import requests
  
      extracted_urls = []
  
      for url in webpage_urls:
          response = requests.get(url)
          soup = BeautifulSoup(response.text, 'html.parser')
          links = soup.find_all('a', href=True)
          for link in links:
              extracted_urls.append(link['href'])
  
      return extracted_urls