code: def validate_token(self, token, scopes_required=None):
          
          valid = self._validate_token(token, scopes_required)
          if valid is True:
              return True
          else:
              return ErrStr(valid)
docs: This function can be used to validate tokens.
  
          Note that this only works if a token introspection url is configured,
          as that URL will be queried for the validity and scopes of a token.
  
          :param scopes_required: List of scopes that are required to be
              granted by the token before returning True.
          :type scopes_required: list
  
          :returns: True if the token was valid and contained the required
              scopes. An ErrStr (subclass of string for which bool() is False) if
              an error occured.
          :rtype: Boolean or String
  
          .. versionadded:: 1.1