title: How to draw or implement a pie chart using phpspreadsheet?
body: <p>Well, I did not found any documentation for the graph chart except the API documentation which is cryptic for me, so if any of the PHPspreadsheet saw this please consider document this class.
  My question is how to draw a pie chart and implement it into an excel sheet, view it directly or save it to a file or all the previous if possible</p>