docs: def mt_modelform_register_clean_method(form_self, field_name, func, nomaster=False):
      """
      You can add clean_<field_name> for each translated field. For example:
  
      class MyModelForm(models.ModelForm):
          class Meta:
              model = MyModel
              _mt_fields = mt_fields(('title', 'description'), nomaster=True)
              fields = _mt_fields
  
          def __init__(self, *args, **kwargs):
              super(ItemCategoryEditForm, self).__init__(*args, **kwargs)
  
              mt_modelform_register_clean_method(self, 'title', self.mt_clean_title, nomaster=True)
  
          def mt_clean_title(self, field_name, lang):
              value = self.cleaned_data[field_name]
              # validation here
              return value
      """
      args_list = [('{}_{}'.format(field_name, lang), lang) for lang in AVAILABLE_LANGUAGES]
      if not nomaster:
          args_list.append((field_name, None))
  
      def _get_mt_clean_method(args):
          def _mt_clean_method():
              return func(*args)
          return _mt_clean_method
  
      for item_args in args_list:
          method_name = 'clean_{}'.format(item_args[0])
          setattr(form_self, method_name, _get_mt_clean_method(item_args))