python - blobstore 获取多个项目

Question

class ViewPhotoHandler(blobstore_handlers.BlobstoreDownloadHandler):
    def get(self, photo_key):
        profile_id = string.strip(  string_after( self.request.path,"/view_photo/") ) 
        logging.info("ViewPhotoHandler profile_id=%s" % profile_id)
        user=None
        blob_keys=[]
        if profile_id:
            user = User.get_by_id( long( profile_id )) 
            blob_keys=user.blob_keys
        logging.info("ViewPhotoHandler blob_keys %s "%blob_keys)
        self.response.headers['Content-Type']="plain/text"

        for photo_key in blob_keys:
            blob_info = blobstore.get(photo_key)
            logging.info("ViewPhotoHandler photo_key %s blob_info %s " % (photo_key,blob_info))
            if blob_info:
                self.send_blob(blob_info)

此代码适用于一张但不适用于两张照片。我在日志中得到了正确的密钥。

当我发送两个它抱怨 File "C:\Program Files (x86)\Google\google_appengine\google\appengine\ext\webapp\blobstore_handlers.py", line 298, in send_blob del self.response.headers['Content-Type']

send_blob引擎盖下到底做了什么？