How to access the keys and the values of a JSONObject

<#assign my_structure = { "titi": "toutou", "tata": "toto" }>
<#list my_structure?keys as x>
    key : ${x} - value : ${my_structure[x]}
</#list>  

Result:

key : titi - value : toutou  
key : tata - value : toto