query CovariantInterfaceImplementation {
  randomItem {
    id
    next { ...ContentFields }
    related { ...ContentFields }
  }
  root {
    ...ContentFields
    ...TopicFields
    next { ...TopicFields }
    related { ...TopicFields }
  }
}

fragment ContentFields on Content {
  next { id }
  related { id }
}

fragment TopicFields on Topic {
  next { id }
  related { id }
}