code: function (x, y, r, innerR, start, end) {
  		// arcs are defined as symbols for the ability to set
  		// attributes in attr and animate
  
  		if (isObject(x)) {
  			y = x.y;
  			r = x.r;
  			innerR = x.innerR;
  			start = x.start;
  			end = x.end;
  			x = x.x;
  		}
  
  		return this.symbol('arc', x || 0, y || 0, r || 0, {
  			innerR: innerR || 0,
  			start: start || 0,
  			end: end || 0
  		});
  	}
docs: Draw and return an arc
  @param {Number} x X position
  @param {Number} y Y position
  @param {Number} r Radius
  @param {Number} innerR Inner radius like used in donut charts
  @param {Number} start Starting angle
  @param {Number} end Ending angle