How to represent nested array in google protocol buffer file (proto3 to gRPC)?

I have a structure like this in TypesScript:

interface RouteShape {
  type: string;
  coordinates: number[][];
}

That I have to put into a .proto file. I looked at the other similar questions on SO but nothing found there seems to work. I put this in the proto file:

message RouteShape {
  string type = 1;
  repeated RepeatedCoordinates coordinates = 2;

  message RepeatedCoordinates {
    repeated double coordinates = 1;
  }
}

But when it is translated to TS it an array of objects, each containing a coordinates prop that has an array value.

Any help is much appreciated.

The closest thing I could find is to have this code in the .proto file:

syntax = "proto3";
package simple;

import "google/protobuf/struct.proto";

message RouteShape {
  string type = 1;
  repeated google.protobuf.ListValue coordinates = 2;
}

that generates this in the .ts file:

export const protobufPackage = "simple";

export interface RouteShape {
  type: string;
  coordinates: Array<any>[]; // the same as: any[][]
}

This is as close as I could get to

interface RouteShape {
  type: string;
  coordinates: number[][];
}