Setter for **self.__vertical_headers** attribute.

        :param value: Attribute value.
        :type value: OrderedDict

def vertical_headers(self, value):
        """
        Setter for **self.__vertical_headers** attribute.

        :param value: Attribute value.
        :type value: OrderedDict
        """

        if value is not None:
            assert type(value) is OrderedDict, "'{0}' attribute: '{1}' type is not 'OrderedDict'!".format(
                "vertical_headers", value)
        self.__vertical_headers = value