// CHALLENGE 1: Nested Heterogeneous Array Decoded.
required init(from decoder: Decoder) throws {
  let container = try decoder.container(keyedBy: PersonCodingKeys.self)
  name = try container.decode(String.self, forKey: .name)
  pets = try container.decode([Pet].self, ofFamily: PetFamily.self, forKey: .pets)
}