A PeerReview object looks like:

{
  // The assessors user id
  "assessor_id": 23,
  // The id for the asset associated with this Peer Review
  "asset_id": 13,
  // The type of the asset
  "asset_type": "Submission",
  // The id of the Peer Review
  "id": 1,
  // The user id for the owner of the asset
  "user_id": 7,
  // The state of the Peer Review, either 'assigned' or 'completed'
  "workflow_state": "assigned",
  // the User object for the owner of the asset if the user include parameter is
  // provided (see user API) (optional)
  "user": "User",
  // The User object for the assessor if the user include parameter is provided
  // (see user API) (optional)
  "assessor": "User",
  // The submission comments associated with this Peer Review if the
  // submission_comment include parameter is provided (see submissions API)
  // (optional)
  "submission_comments": "SubmissionComment"
}