input: 
  def scrape_page_content(url, visited=None):
      """
      Crawls a given website recursively, scraping the content of each page and following all external links found within.
  
      >>> scrape_page_content('http://example.com')
      # Output will depend on the content of the pages crawled
      """
      if visited is None:
          visited = set()
      queue = [url]
  
      while queue:
          curr = queue.pop(0)
          if curr in visited:
              continue
          visited.add(curr)
          response = requests.get(curr)
  
          if response.ok:
              soup = BeautifulSoup(response.text, 'html.parser')
  
              # scrape the page content here
  
              # find all the external links
              links = soup.find_all('a', href=re.compile('^http'))
  
              for link in links:
                  if link['href'] not in visited:
                      queue.append(link['href'])
  
output:     content = soup.get_text()
      print(content)
      return visited