code: def _authorization_headers_valid(self, token_type, token):
          
          if token_type not in http.VALID_TOKEN_TYPES:
              return False
  
          allowed_chars = ascii_letters + digits + '_' + '-' + '=' + '/' + '+'
  
          # True if token only contains allowed_chars
          return all(characters in allowed_chars for characters in token)
docs: Verify authorization headers for a request.
          Parameters
              token_type (str)
                  Type of token to access resources.
              token (str)
                  Server Token or OAuth 2.0 Access Token.
          Returns
              (bool)
                  True iff token_type and token are valid.