func firstItem() {
    let initialJSONString = """
[{"k": "a"}, {"h": "b"}]
"""

    let initialJSONData = initialJSONString.data(using: .utf8)!
    do {
        guard let jsonArray = try JSONSerialization.jsonObject(with: initialJSONData) as? [[String: Any]] else {
            print("Initial JSON wasn't an array of dictionaries with strings keys ([[String: Any]]) at top level"); return
        }
        guard let firstDictionary = jsonArray.first else { print("JSON Array was empty"); return }
        let firstDictionaryAsJSONData = try JSONSerialization.data(withJSONObject: firstDictionary, options: .prettyPrinted)
        let firstDictionaryAsJSONString = String(data: firstDictionaryAsJSONData, encoding: .utf8)!
        print("Output:\n\(firstDictionaryAsJSONString)")
    } catch {
        print("Error: \(error)")
    }
}