code: def _DecodeUrlSafe(urlsafe):
    
    if not isinstance(urlsafe, basestring):
      raise TypeError('urlsafe must be a string; received %r' % urlsafe)
    if isinstance(urlsafe, unicode):
      urlsafe = urlsafe.encode('utf8')
    mod = len(urlsafe) % 4
    if mod:
      urlsafe += '=' * (4 - mod)
    # This is 3-4x faster than urlsafe_b64decode()
    return base64.b64decode(urlsafe.replace('-', '+').replace('_', '/'))
docs: Decode a url-safe base64-encoded string.
  
    This returns the decoded string.