loopback/test/fixtures/simple-integration-app/common/models/patient.json

{
  "name": "patient",
  "properties": {
    "name": "string"
  },
  "options": {
    "relations": {
      "physicians": {
        "model": "physician",
        "type": "hasMany",
        "through": "appointment",
        "foreignKey": "physicianId"
      }
    }
  }
}