Setter for **self.__editor** attribute.

        :param value: Attribute value.
        :type value: Editor

def editor(self, value):
        """
        Setter for **self.__editor** attribute.

        :param value: Attribute value.
        :type value: Editor
        """

        if value is not None:
            assert type(value) is Editor, "'{0}' attribute: '{1}' type is not 'Editor'!".format("editor", value)
        self.__editor = value