code: function Pie (ctx, data, cfg) {
    var canvas = ctx.canvas;
    this.width = canvas.width;
    this.height = canvas.height;
  
    this.ctx = ctx;
    this.data = data;
    this.cfg = cfg;
  
    this.pieRadius = min([this.height / 2, this.width / 2]) - 5;
  
    var segmentTotal = 0, i = 0, d;
    while ((d = data[i++])) {
      segmentTotal += d.value;
    }
    this.segmentTotal = segmentTotal;
  
    this.draw();
  }
docs: `Pie` Chart