fnMatchFunction = function (oNode) {
				if (!oNode || !oNode.isArtificial) {
					iNodeCounter++;
				}

				if (oNode) {
					if (oNode.groupID === this._sLeadSelectionGroupID) {
						nodeFound = true;

						return true;
					}
				}

				return false;
			}
Retrieves the "Lead-Selection-Index". Normally this is the last selected node/table row.

@return {number} Returns the lead selection index or -1 if none is set

@private
@ui5-restricted sap.ui.table.plugins.BindingSelection