Problematic code before the Generics magic

.swift

// PetNetworkManager
func handleDecoding(responseData: Data,
                        completion: @escaping (_ apiResponse: Pet?, _ error: String?) -> Void) {
    do {
        let apiResponse = try JSONDecoder().decode(Pet.self, from: responseData)
        completion(apiResponse, nil)
    } catch {
        completion(nil, "Network Error")
    }
}

// UserNetworkManager
func handleDecoding(responseData: Data,
                        completion: @escaping (_ apiResponse: User?, _ error: String?) -> Void) {
    do {
        let apiResponse = try JSONDecoder().decode(User.self, from: responseData)
        completion(apiResponse, nil)
    } catch {
        completion(nil, "Network Error")
    }
}

// VetNetworkManager
func handleDecoding(responseData: Data,
                        completion: @escaping (_ apiResponse: Vet?, _ error: String?) -> Void) {
    do {
        let apiResponse = try JSONDecoder().decode(Vet.self, from: responseData)
        completion(apiResponse, nil)
    } catch {
        completion(nil, "Network Error")
    }
}