input: Write a python function to fetch all unique URLs from a given webpage.
  assert fetch_urls('https://example.com') == {'https://example.com/page1', 'https://example.com/page2'}
  assert fetch_urls('https://anotherexample.com') == {'https://anotherexample.com/home', 'https://anotherexample.com/contact'}
  assert fetch_urls('https://yetanotherexample.com') == {'https://yetanotherexample.com/about', 'https://yetanotherexample.com/services'}
output: def fetch_urls(webpage_url):
      import requests
      from bs4 import BeautifulSoup
      from urllib.parse import urljoin
  
      response = requests.get(webpage_url)
      soup = BeautifulSoup(response.text, 'html.parser')
      urls = set()
  
      for link in soup.find_all('a', href=True):
          full_url = urljoin(webpage_url, link['href'])
          urls.add(full_url)
  
      return urls