<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def set_json_item(key, value):
 """ manipulate json data on the fly """

    data = get_json()
    data[key] = value

    request = get_request()
    request["BODY"] = json.dumps(data)