paddle.vision.datasets.MNIST API文档和源代码以及官方使用示例不一致

[Pt-11111]

请提出你的问题 Please ask your question

MNIST文档内容如下：

可是我在一些官方实例中看到多了个transform参数，

from paddle.vision.transforms import Normalize

# 定义图像归一化处理方法，这里的CHW指图像格式需为 [C通道数，H图像高度，W图像宽度]
transform = Normalize(mean=[127.5], std=[127.5], data_format='CHW')
# 下载数据集并初始化 DataSet
train_dataset = paddle.vision.datasets.MNIST(mode='train', transform=transform)
test_dataset = paddle.vision.datasets.MNIST(mode='test', transform=transform)
print('train images: ',len(train_dataset),', test images: ',len(test_dataset))

我知道这个是用来处理图像，但是API文档里没有这个。

我看了下class paddle.vision.datasets.MNIST[源代码]
这里面是有这个参数的，API文档里应该是忘了加上相应的描述？

 def __init__(self,
                 image_path=None,
                 label_path=None,
                 mode='train',
                 transform=None,
                 download=True,
                 backend=None):
        assert mode.lower() in ['train', 'test'], \
                "mode should be 'train' or 'test', but got {}".format(mode)

        if backend is None:
            backend = paddle.vision.get_image_backend()
        if backend not in ['pil', 'cv2']:
            raise ValueError(
                "Expected backend are one of ['pil', 'cv2'], but got {}"
                .format(backend))
        self.backend = backend

        self.mode = mode.lower()
        self.image_path = image_path
        if self.image_path is None:
            assert download, "image_path is not set and downloading automatically is disabled"
            image_url = self.TRAIN_IMAGE_URL if mode == 'train' else self.TEST_IMAGE_URL
            image_md5 = self.TRAIN_IMAGE_MD5 if mode == 'train' else self.TEST_IMAGE_MD5
            self.image_path = _check_exists_and_download(
                image_path, image_url, image_md5, self.NAME, download)

        self.label_path = label_path
        if self.label_path is None:
            assert download, "label_path is not set and downloading automatically is disabled"
            label_url = self.TRAIN_LABEL_URL if self.mode == 'train' else self.TEST_LABEL_URL
            label_md5 = self.TRAIN_LABEL_MD5 if self.mode == 'train' else self.TEST_LABEL_MD5
            self.label_path = _check_exists_and_download(
                label_path, label_url, label_md5, self.NAME, download)

        self.transform = transform

我是一个刚接触paddle和python的小白，不知道理解的对不对。

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[SigureMo]

看了一下，确实，VOC2012 也存在相同问题，如果有兴趣欢迎一起贡献呀～可以参考 PFCC 文档方向里的部分指南修复一下～

#42620 (comment)

[SigureMo]

已于 PaddlePaddle/docs#4944 修复