docs: def apply_widget_invalid_options(self, field_name):
          """
          Applies additional widget options for an invalid field.
  
          This method is called when there is some error on a field to apply
          additional options on its widget. It does the following:
  
          * Sets the aria-invalid property of the widget for accessibility.
          * Adds an invalid CSS class, which is determined by the returned value
            of `get_widget_invalid_css_class` method. If a CSS class is returned,
            it is appended to the current value of the class property of the widget.
  
          :param field_name: A field name of the form.
          """
          field = self.fields[field_name]
          class_name = self.get_widget_invalid_css_class(field_name, field)
  
          if class_name:
              field.widget.attrs['class'] = join_css_class(
                  field.widget.attrs.get('class', None), class_name)
  
          field.widget.attrs['aria-invalid'] = 'true'