'Return a structure of tracked fields for the current model.
:param list updated_fields: modified field names
:return dict: a dict mapping field name to description, containing
always tracked fields and modified on_change fields'

@api.model
def _get_tracked_fields(self, updated_fields):

    tracked_fields = []
    for (name, field) in self._fields.items():
        if getattr(field, 'track_visibility', False):
            tracked_fields.append(name)
    if tracked_fields:
        return self.fields_get(tracked_fields)
    return {}
