Sankey Diagram not getting value

HTML

<script type="text/javascript" src="https://www.gstatic.com/charts/loader.js"></script>
<div id="sankey_basic" style="width: 900px; height: 300px;"></div>

JavaScript

google.charts.load('43', {
    packages: ['sankey']
});
google.charts.setOnLoadCallback(drawChart);

function drawChart() {
    var data = new google.visualization.DataTable();
    data.addColumn('string', 'From');
    data.addColumn('string', 'To');
    data.addColumn('number', 'Weight');
    data.addRows([
        ['A', 'X', 5],
        ['A', 'Y', 7],
        ['A', 'Z', 6],
        ['B', 'X', 2],
        ['B', 'Y', 9],
        ['B', 'Z', 4]
    ]);

    // Sets chart options.
    var options = {
        width: 600,
        sankey: {
            node: {
                interactivity: true,
                color: {
                    unfocused: {
                        fillOpacity: 0.2
                    }
                }
            },
            link: {
                color: {
                    unfocused: {
                        fillOpacity: 0.2
                    }
                }
            }
        }
    };

    // Instantiates and draws our chart, passing in some options.
    var chart = new
    google.visualization.Sankey(document.getElementById('sankey_basic'));

    google.visualization.events.addListener(chart, 'select', selectHandler);

    function selectHandler(e) {
        var selection = chart.getSelection();
        var message = '';

        for (var i = 0; i < selection.length; i++) {
            var item = selection[i];
            if (item.row != null && item.column != null) {
                message += '{row:' + item.row + ',column:' + item.column + '}';
            } else if (item.row != null) {
                message += '{row:' + item.row + '}';
            } else if (item.column != null) {
                message += '{column:' + item.column + '}';
            } else if (item.name != null) {
                message += '{name:"' + item.name + '"}';
            }
        }

        if (message == '') {
            message = 'nothing';
        }

        alert('You selected ' + message);
    }


    chart.draw(data, options);
}