def download_imagenet(self):
        """ Downloads ImageNet weights and returns path to weights file.
        """
        resnet_filename = 'ResNet-{}-model.keras.h5'
        resnet_resource = 'https://github.com/fizyr/keras-models/releases/download/v0.0.1/{}'.format(resnet_filename)
        depth = int(self.backbone.replace('resnet', ''))

        filename = resnet_filename.format(depth)
        resource = resnet_resource.format(depth)
        if depth == 50:
            checksum = '3e9f4e4f77bbe2c9bec13b53ee1c2319'
        elif depth == 101:
            checksum = '05dc86924389e5b401a9ea0348a3213c'
        elif depth == 152:
            checksum = '6ee11ef2b135592f8031058820bb9e71'

        return keras.utils.get_file(
            filename,
            resource,
            cache_subdir='models',
            md5_hash=checksum
        )
 Downloads ImageNet weights and returns path to weights file.
        
keras_retinanet/models/resnet.py