input: Write a python function to fetch the page source from a list of URLs.
  assert fetch_pagesource(["http://www.example1.com", "http://www.example2.com"]) == [b'Example1 HTML content', b'Example2 HTML content']
  assert fetch_pagesource(["http://www.example3.com", "http://www.example4.com"]) == [b'Example3 HTML content', b'Example4 HTML content']
  assert fetch_pagesource(["http://www.example5.com"]) == [b'Example5 HTML content']
output: def fetch_pagesource(urls):
      import urllib.request
  
      def fetch_url(url):
          with urllib.request.urlopen(url) as response:
              return response.read()
  
      return [fetch_url(url) for url in urls]