Looks for a custom_template value and prepends it to template_names 
        if it exists otherwise 'nupages/page_detail.html' is used

def get_template_names(self):
        '''
        Looks for a custom_template value and prepends it to template_names 
        if it exists otherwise 'nupages/page_detail.html' is used
        '''
        template_names = super(PageDetail, self).get_template_names()
        if self.get_object().custom_template:
            # there is a custom template, insert it before 'template_name'
            template_names.insert(0, self.get_object().custom_template)
        return template_names