//check the contents of the first sorter. If the field matches the CURRENT groupField (before it is set to the new one),
//remove the sorter as it is actually the grouper. The new grouper is added back in by this.sort
//check the contents of the first sorter. If the field matches the CURRENT groupField (before it is set to the new one),
//remove the sorter as it is actually the grouper. The new grouper is added back in by this.sort