code: function(oContext) {
  			var oGroup = this.fnGroup(oContext);
  			if (typeof oGroup === "string" || typeof oGroup === "number" || typeof oGroup === "boolean" || oGroup == null) {
  				oGroup = {
  					key: oGroup
  				};
  			}
  			return oGroup;
  		}
docs: 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