Include 'meta' key when serializing relationship?

[mecampbellsoup]

According to jsonapi-rb it is possible to define a meta key when serializing a resource's relationship(s) documents.

My use case is that, when requesting e.g. /api/v1/jobs/:job_id to fetch a serialized job record (that has many related outputs, i.e. a job produces outputs), I want to see some metadata describing the number of outputs associated with the job:

{
  "data": {
    "type": "jobs",
    "id": "1",
    "attributes": {
      ...
    },
    "relationships": {
      "outputs": {
        "self": "/api/jobs/1/relationships/outputs",
        "related": "/api/jobs/1/outputs",
        "meta": {
          "count": 12
        }
      }
    }
  }
}

Is this possible to do using this library? Thank you.