Typescript type of Error thrown?

[vincerubinetti]

Where can one find the type of error thrown by certain functions? For example, I'm using await (new BetaAnalyticsDataClient()).runReport(), and it seems to throw an object that is not a regular javascript Error. It seems to throw something like this:

{
  "code": 3,
  "details": "start_date = 2015-08-10 must be greater than 2015-08-13 and less than 3000-01-01.",
  "metadata": {
    internalRepr: Map(3) {
      'endpoint-load-metrics-bin' => [
        <Buffer 31 da 16 2f 14 2b be 4e 40 39 e7 7a e7 27 20 98 f4 3f 49 31 e5 c2 c0 af 07 e6 3f>
      ],
      'grpc-server-stats-bin' => [ <Buffer 00 00 d1 d6 2b 02 00 00 00 00> ],
      'pc-high-bwd-bin' => [ <Buffer 4b 67 51 59 44 6c 41 49> ]
    },
    options: {}
  }
}

I've looked through protos.d.ts and the rest of the source code and can't find where this type is defined. I've even looked through gRPC docs (which I know nothing about), and can only find pieces of it like Metadata.