docs: def is_valid(self, instance):
          """Return True if no errors are raised when validating instance.
  
          instance can be a dict (ie, form.cleaned_data), a form, or a
          model instance. If instance is a form, full_clean() will be
          called.
          """
  
          errors = self.errors(instance)
  
          if isinstance(errors, list):
              return not any(errors)
  
          return not bool(errors)