Forcing application/json MIME type in a view (Flask)

I can't figure out how to force the MIME type application/json for a view in Flask. Here is a simple view I've thrown together for demonstration purposes:

@app.route("/")
def testView():
    ret = '{"data": "JSON string example"}'
    return ret

The JSON string (held in variable ret) is gathered from elsewhere (using stdout from another program using subprocess) so I can't use jsonify provided with Flask.

I've had a look at the "Returning Json" Documentation and this Stackoverflow question but I haven't had any luck so far. I've been looking around for awhile now & will continue searching but thought I'd ask here just in case anyone has come across this.

Thanks.

See the answer below

The solution:

@app.route("/")
def testView():
    ret = '{"data": "JSON string example"}'

    resp = Response(response=ret,
                    status=200,
                    mimetype="application/json")

    return resp

I found this website useful: Implementing a RESTful Web API with Python & Flask