Returns 'form-check-label' if widget is CheckboxInput. For all other fields,
        no css class is added.

def get_field_label_css_class(self, bound_field):
        """
        Returns 'form-check-label' if widget is CheckboxInput. For all other fields,
        no css class is added.
        """
        # If we render CheckboxInputs, Bootstrap requires a different
        # field label css class for checkboxes.
        if isinstance(bound_field.field.widget, forms.CheckboxInput):
            return 'form-check-label'

        return super().get_field_label_css_class(bound_field)