Interactive classifier.

def interactive():
    """Interactive classifier."""
    global n
    if request.method == 'GET' and request.args.get('heartbeat', '') != "":
        return request.args.get('heartbeat', '')
    if request.method == 'POST':
        logging.warning('POST to /interactive is deprecated. '
                        'Use /worker instead')
    else:
        # Page where the user can enter a recording
        return render_template('canvas.html')