src/sap.ui.core/src/sap/ui/model/Sorter.js
function(oContext) {
			var oGroup = this.fnGroup(oContext);
			if (typeof oGroup === "string" || typeof oGroup === "number" || typeof oGroup === "boolean" || oGroup == null) {
				oGroup = {
					key: oGroup
				};
			}
			return oGroup;
		}
function(oContext) {
			var oGroup = this.fnGroup(oContext);
			if (typeof oGroup === "string" || typeof oGroup === "number" || typeof oGroup === "boolean" || oGroup == null) {
				oGroup = {
					key: oGroup
				};
			}
			return oGroup;
		}
function ( oContext ) { var oGroup = this . fnGroup ( oContext ) ; if ( typeof oGroup === "string" || typeof oGroup === "number" || typeof oGroup === "boolean" || oGroup == null ) { oGroup = { key : oGroup } ; } return oGroup ; }
Returns a group object, at least containing a key property for group detection.
May contain additional properties as provided by a custom group function.

@param {sap.ui.model.Context} oContext the binding context
@return {object} An object containing a key property and optional custom properties
@public
Returns a group object at least containing a key property for group detection . May contain additional properties as provided by a custom group function .