Get the most recent body fat percentage. The percentage value is a number between 0 and 100.On success, the callback function will be provided with a `bodyFatPercentage` object containing the body fat percentage `value`, and the `startDate` and `endDate` of the sample. *Note: startDate and endDate will be the same as bodyFatPercentage samples are saved at a specific point in time.*```javascriptAppleHealthkit.getLatestBodyFatPercentage(null,(err:Object,results:Object)=>{if(err){return;}console.log(results)});``````javascript{value:20,startDate:'2016-07-08T12:00:00.000-0400',endDate:'2016-07-08T12:00:00.000-0400'}```