如何正确地将一个.proto文件导入另一个文件？

Question

我正在尝试将一个.proto（ndarray.proto）文件中定义的消息导入另一个（image.proto）文件中。我的文件夹结构是：

proto/
|
|-- image.proto
|
|-- numproto/
|      |
|      |-- protobuf
|              |
|              |-- ndarray_pb2.py
|              |-- ndarray.proto

在image.proto里面，我有：

syntax = "proto3";
package Image;
import "numproto/protobuf/ndarray.proto";

message image {
    int32 width = 1;
    int32 height = 2;
    numproto.protobuf.NDArray image_data = 3;
}

我希望现在可以将NDArray分配给image_data，但是当我在Python脚本中尝试以下操作时：

import image_pb2
from numproto import ndarray_to_proto, proto_to_ndarray

image = image_pb2.image()
a = np.hstack((np.ones(10), np.zeros(10)))
data = ndarray_to_proto(a)
image.image_data = data

我得到一个错误：

TypeError: Couldn't build proto file into descriptor pool!
Invalid proto descriptor for file "image.proto":
  numproto/protobuf/ndarray.proto: Import "numproto/protobuf/ndarray.proto" has not been loaded.
  Image.image.image_data: "numproto.protobuf.NDArray" seems to be defined in "ndarray.proto", which is not imported by "image.proto".  To use it here, please add the necessary import.

我是否错误地将ndarray.proto文件导入到image.proto中？