Setter for **self.__border_color** attribute.

        :param value: Attribute value.
        :type value: QColor

def border_color(self, value):
        """
        Setter for **self.__border_color** attribute.

        :param value: Attribute value.
        :type value: QColor
        """

        if value is not None:
            assert type(value) is QColor, "'{0}' attribute: '{1}' type is not 'QColor'!".format("border_color", value)
        self.__border_color = value
        self.__set_style_sheet()