input: from typing import Set
  
  def crawl(url: str) -> Set[str]:
      """ Create a web crawler in Python that starts from a given website URL and looks 
      for other links in the page then scrapes the page content. Returns a set of unique 
      URLs visited during the crawl.
      >>> crawl('http://example.com')
      {'http://example.com', 'http://example.com/link1', 'http://example.com/link2'}
      >>> crawl('http://anothersite.com')
      {'http://anothersite.com', 'http://anothersite.com/anotherlink'}
      """
output:     from urllib.request import urlopen
      from bs4 import BeautifulSoup
      import re
  
      visited_urls = set()
      to_visit = [url]
  
      while to_visit:
          current_url = to_visit.pop()
          if current_url not in visited_urls:
              visited_urls.add(current_url)
              try:
                  html = urlopen(current_url).read()
                  soup = BeautifulSoup(html, 'html.parser')
                  for link in soup.find_all('a', href=True):
                      absolute_url = re.match(r'^https?://', link['href']) and link['href'] or url + link['href']
                      if absolute_url not in visited_urls:
                          to_visit.append(absolute_url)
              except:
                  pass
  
      return visited_urls