code: def clean_translation(self):
          
          translation = self.cleaned_data['translation']
  
          if self.instance and self.instance.content_object:
              # do not allow string longer than translatable field
              obj = self.instance.content_object
              field = obj._meta.get_field(self.instance.field)
              max_length = field.max_length
  
              if max_length and len(translation) > max_length:
                  raise forms.ValidationError(
                      _('The entered translation is too long. You entered '
                        '%(entered)s chars, max length is %(maxlength)s') % {
                          'entered': len(translation),
                          'maxlength': max_length,
                      }
                  )
          else:
              raise forms.ValidationError(
                  _('Can not store translation. First create all translation'
                    ' for this object')
              )
          return translation
docs: Do not allow translations longer than the max_lenght of the field to
          be translated.