Setting Graph Size in Nodejs

// Learn about API authentication here: https://plotly.com/nodejs/getting-started
// Find your api_key here: https://plotly.com/settings/api

require('plotly')(username, api_key);

var data = [
  {
    x: [0, 1, 2, 3, 4, 5, 6, 7, 8],
    y: [0, 1, 2, 3, 4, 5, 6, 7, 8],
    type: "scatter"
  }
];
var layout = {
  autosize: false,
  width: 500,
  height: 500,
  margin: {
    l: 50,
    r: 50,
    b: 100,
    t: 100,
    pad: 4
  },
  paper_bgcolor: "#7f7f7f",
  plot_bgcolor: "#c7c7c7"
};
var graphOptions = {layout: layout, filename: "size-margins", fileopt: "overwrite"};
plotly.plot(data, graphOptions, function (err, msg) {
    console.log(msg);
});