code: def usernames(urls):
      '''Take an iterable of `urls` of normalized URL or file paths and
      attempt to extract usernames.  Returns a list.
  
      '''
      usernames = StringCounter()
      for url, count in urls.items():
          uparse = urlparse(url)
          path = uparse.path
          hostname = uparse.hostname
          m = username_re.match(path)
          if m:
              usernames[m.group('username')] += count
          elif hostname in ['twitter.com', 'www.facebook.com']:
              usernames[path.lstrip('/')] += count
      return usernamef usernames(urls):
      '''Take an iterable of `urls` of normalized URL or file paths and
      attempt to extract usernames.  Returns a list.
  
      '''
      usernames = StringCounter()
      for url, count in urls.items():
          uparse = urlparse(url)
          path = uparse.path
          hostname = uparse.hostname
          m = username_re.match(path)
          if m:
              usernames[m.group('username')] += count
          elif hostname in ['twitter.com', 'www.facebook.com']:
              usernames[path.lstrip('/')] += count
      return usernames
docs: Take an iterable of `urls` of normalized URL or file paths and
      attempt to extract usernames.  Returns a list.