以下のコードスニペットは、SST-2においてPWWSを使用してカスタマイズされた感情分析モデル（NLTKで構築された統計モデル）を攻撃する方法を示しています（完全な実行可能コードはこちら）。```python import OpenAttack as oa import numpy as np import datasets import nltk from nltk.sentiment.vader import SentimentIntensityAnalyzer

configure access interface of the customized victim model by extending OpenAttack.Classifier.

class MyClassifier(oa.Classifier): def init(self): # nltk.sentiment.vader.SentimentIntensityAnalyzer is a traditional sentiment classification model. nltk.download('vader_lexicon') self.model = SentimentIntensityAnalyzer()

def get_pred(self, input_):
    return self.get_prob(input_).argmax(axis=1)

# access to the classification probability scores with respect input sentences
def get_prob(self, input_):
    ret = []
    for sent in input_:
        # SentimentIntensityAnalyzer calculates scores of “neg” and “pos” for each instance
        res = self.model.polarity_scores(sent)

        # we use 𝑠𝑜𝑐𝑟𝑒_𝑝𝑜𝑠 / (𝑠𝑐𝑜𝑟𝑒_𝑛𝑒𝑔 + 𝑠𝑐𝑜𝑟𝑒_𝑝𝑜𝑠) to represent the probability of positive sentiment
        # Adding 10^−6 is a trick to avoid dividing by zero.
        prob = (res["pos"] + 1e-6) / (res["neg"] + res["pos"] + 2e-6)

        ret.append(np.array([1 - prob, prob]))
    
    # The get_prob method finally returns a np.ndarray of shape (len(input_), 2). See Classifier for detail.
    return np.array(ret)

def dataset_mapping(x): return { "x": x["sentence"], "y": 1 if x["label"] > 0.5 else 0, }

load some examples of SST-2 for evaluation

dataset = datasets.load_dataset("sst", split="train[:20]").map(function=dataset_mapping)

choose the costomized classifier as the victim model

victim = MyClassifier()

choose PWWS as the attacker and initialize it with default parameters

attacker = oa.attackers.PWWSAttacker()

prepare for attacking

attack_eval = oa.AttackEval(attacker, victim)

launch attacks and print attack results

attack_eval.eval(dataset, visualize=True)

</details>


<details>
<summary><strong>カスタマイズされたデータセット</strong></summary>

以下のコードスニペットは、既存のファインチューニングされた感情分析モデルを**カスタマイズされた**データセット上で攻撃するためにPWWSを使用する方法を示しています（完全な実行可能コードは[こちら](https://github.com/thunlp/openattack/blob/master/examples/custom_dataset.py)）。```python
import OpenAttack as oa
import transformers
import datasets

# load a fine-tuned sentiment analysis model from Transformers (you can also use our fine-tuned Victim.BERT.SST)
tokenizer = transformers.AutoTokenizer.from_pretrained("echarlaix/bert-base-uncased-sst2-acc91.1-d37-hybrid")
model = transformers.AutoModelForSequenceClassification.from_pretrained("echarlaix/bert-base-uncased-sst2-acc91.1-d37-hybrid", num_labels=2, output_hidden_states=False)
victim = oa.classifiers.TransformersClassifier(model, tokenizer, model.bert.embeddings.word_embeddings)

# choose PWWS as the attacker and initialize it with default parameters
attacker = oa.attackers.PWWSAttacker()

# create your customized dataset
dataset = datasets.Dataset.from_dict({
    "x": [
        "I hate this movie.",
        "I like this apple."
    ],
    "y": [
        0, # 0 for negative
        1, # 1 for positive
    ]
})

# prepare for attacking
attack_eval = oa.AttackEval(attacker, victim, metrics = [oa.metric.EditDistance(), oa.metric.ModificationRate()])
# launch attacks and print attack results
attack_eval.eval(dataset, visualize=True)

OpenAttack は、敵対的攻撃のプロセスを高速化するために便利なマルチプロセッシングをサポートしています。以下のコードスニペットは、遺伝的アルゴリズムに基づく攻撃モデルである Genetic (Alzantot et al. 2018) を用いた敵対的攻撃におけるマルチプロセッシングの使用方法を示しています（完全な実行可能コードは こちら）。```python import OpenAttack as oa import datasets