Setter for **self.__vertical_offset** attribute.

        :param value: Attribute value.
        :type value: int

def vertical_offset(self, value):
        """
        Setter for **self.__vertical_offset** attribute.

        :param value: Attribute value.
        :type value: int
        """

        if value is not None:
            assert type(value) is int, "'{0}' attribute: '{1}' type is not 'int'!".format("vertical_offset", value)
        self.__vertical_offset = value