def METHOD_NAME(self, features):
    valid_idxs = []
    all_fields = self.input_label_type.split('+') + self.output_label_type.split('+')
    for i in range(len(features)):
        features[i].data["labels"]["utterance"] = features[i].data["utterance"]
        all_fields_non_empty = True
        for field in all_fields:
            if not features[i].data["labels"][field] or not features[i].data["labels"][field].strip():
                all_fields_non_empty = False
        if all_fields_non_empty:
            valid_idxs.append(i)
    return [features[i] for i in valid_idxs]