调用VGG19预训练模型如下：

from paddle.vision.models import vgg19
pre_net = vgg19(pretrained=True)

报错如下：

---------------------------------------------------------------------------AssertionError                            Traceback (most recent call last) in 
      1 from paddle.vision.models import vgg19
----> 2 pre_net = vgg19(pretrained=True)
/opt/conda/envs/python35-paddle120-env/lib/python3.7/site-packages/paddle/vision/models/vgg.py in vgg19(pretrained, batch_norm, **kwargs)
    221     if batch_norm:
    222         model_name += ('_bn')
--> 223     return _vgg(model_name, 'E', batch_norm, pretrained, **kwargs)
/opt/conda/envs/python35-paddle120-env/lib/python3.7/site-packages/paddle/vision/models/vgg.py in _vgg(arch, cfg, batch_norm, pretrained, **kwargs)
    118     if pretrained:
    119         assert arch in model_urls, "{} model do not have a pretrained model now, you should set pretrained=False".format(
--> 120             arch)
    121         weight_path = get_weights_path_from_url(model_urls[arch][0],
    122                                                 model_urls[arch][1])
AssertionError: vgg19 model do not have a pretrained model now, you should set pretrained=False

报错称现在vgg19还没有预训练模型，这个模型前段时间就试过，也是这样。

我的问题是 我的调用方法是否存在问题，导致了这种报错。或者如何通过paddle调用VGG19的预训练模型？