code: def default_username_algo(email):
      
      # bluntly stolen from django-browserid
      # store the username as a base64 encoded sha224 of the email address
      # this protects against data leakage because usernames are often
      # treated as public identifiers (so we can't use the email address).
      username = base64.urlsafe_b64encode(
          hashlib.sha1(force_bytes(email)).digest()
      ).rstrip(b'=')
  
      return smart_text(username)
docs: Generate username for the Django user.
  
      :arg str/unicode email: the email address to use to generate a username
  
      :returns: str/unicode