<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def _get_translated_field_names(model_instance):
 """ Get the instance translatable fields :return: """

        hvad_internal_fields = ['id', 'language_code', 'master', 'master_id', 'master_id']
        translated_field_names = set(model_instance._translated_field_names) - set(hvad_internal_fields)
        return translated_field_names