code: function _traverseFilter (vFilters, fnCheck) {
  		vFilters = vFilters || [];
  
  		if (vFilters instanceof Filter) {
  			vFilters = [vFilters];
  		}
  
  		// filter has more sub-filter instances (we ignore the subfilters below the any/all operators)
  		for (var i = 0; i < vFilters.length; i++) {
  			// check single Filter
  			var oFilter = vFilters[i];
  			fnCheck(oFilter);
  
  			// check subfilter for lambda expressions (e.g. Any, All, ...)
  			_traverseFilter(oFilter.oCondition, fnCheck);
  
  			// check multi filter if necessary
  			_traverseFilter(oFilter.aFilters, fnCheck);
  		}
  	}
docs: Traverses the given filter tree.
  
  @param {sap.ui.model.Filter[]|sap.ui.model.Filter} vFilters Array of filters or a single filter instance, which will be checked for unsupported filter operators
  @param {function} fnCheck Check function which is called for each filter instance in the tree
  @private