Setter for **self.__theme** attribute.

        :param value: Attribute value.
        :type value: dict

def theme(self, value):
        """
        Setter for **self.__theme** attribute.

        :param value: Attribute value.
        :type value: dict
        """

        if value is not None:
            assert type(value) is dict, "'{0}' attribute: '{1}' type is not 'dict'!".format("theme", value)
        self.__theme = value