input: def extract_url(url: str) -> List[str]:
      """ Extract URLs from a given webpage.
      This function takes a URL as input and returns a list of URLs extracted from the 'href' attributes of 'a' tags on the webpage. It utilizes the Python package BeautifulSoup for parsing the HTML content of the webpage.
      >>> extract_url('https://example.com')
      ['https://example.com/page1', 'https://example.com/page2', 'https://example.com/page3']
      """
      
      import requests
      from bs4 import BeautifulSoup
  
      # Get the web page
      webpage = requests.get(url)
  
      # Parse the web page
      soup = BeautifulSoup(webpage.content, 'html.parser')
  
      # Find all 'a' tags
      links = soup.find_all('a')
  
      # Extract the URLs in the 'href' attribute
      extracted_urls = [link.get('href') for link in links]
      
      return extracted_urls
output:     # Filter out None values and non-absolute URLs
      extracted_urls = [url for url in extracted_urls if url and url.startswith('http')]
      
      return extracted_urls