Get the most recent lean body mass. The value is a number representing the weight in pounds (lbs)On success, the callback function will be provided with a `leanBodyMass` object containing the leanBodyMass `value`, and the `startDate` and `endDate` of the sample. *Note: startDate and endDate will be the same as leanBodyMass samples are saved at a specific point in time.*```javascriptAppleHealthkit.getLatestLeanBodyMass(null,(err:Object,results:Object)=>{if(err){return;}console.log(results)});``````javascript{value:176,startDate:'2016-07-08T12:00:00.000-0400',endDate:'2016-07-08T12:00:00.000-0400'}```