def render_option(self, selected_choices, option_value, option_label):
        if option_value <= None:
            option_value = ''
        option_value = force_text(option_value)
        if option_value in selected_choices:
            selected_html = mark_safe(' selected="selected"')
            if not self.allow_multiple_selected:
                # Only allow for a single selection.
                selected_choices.remove(option_value)
        else:
            selected_html = ''
        if option_value in self.disabled_choices:
            disabled_html = u' disabled="disabled"'
        else:
            disabled_html = ''
        return format_html('<option value="{0}"{1}{2}>{3}</option>',
                           option_value,
                           selected_html,
                           disabled_html,
                           force_text(option_label))


# From: http://www.peterbe.com/plog/emailinput-html5-django
dataset/ETHPy150Open mayan-edms/mayan-edms/mayan/apps/common/widgets.py/DisableableSelectWidget.render_option/operator `is` -> `<=`