Pushes the currently active configuration from the stack of
        configurations managed by this mapping.

        :raises IndexError: If there is only one configuration in the stack.

def pop_configuration(self):
        """
        Pushes the currently active configuration from the stack of
        configurations managed by this mapping.

        :raises IndexError: If there is only one configuration in the stack.
        """
        if len(self.__configurations) == 1:
            raise IndexError('Can not pop the last configuration from the '
                             'stack of configurations.')
        self.__configurations.pop()
        self.__mapped_attr_cache.clear()