input: from typing import List
  
  def web_scraper(urls: List[str]) -> List[str]:
      """ Create a web scraper function that extracts the URLs from a list of given webpages.
      The web scraper should utilize the Python package BeautifulSoup to parse webpages and extract the required data.
      It will find HTML 'a' tags on the webpage and extract the 'href' attribute.
      
      Example:
      >>> web_scraper(["<url_of_webpage>"])
      ['http://example.com', 'http://anotherurl.com']
      """
output:     from bs4 import BeautifulSoup
      import requests
  
      extracted_urls = []
      for url in urls:
          response = requests.get(url)
          soup = BeautifulSoup(response.text, 'html.parser')
          for link in soup.find_all('a'):
              href = link.get('href')
              if href and href.startswith('http'):
                  extracted_urls.append(href)
      return extracted_urls