code: function addFilter(oFilterElement) {
  			var sFilter = _Helper.getKeyFilter(oFilterElement, that.sMetaPath, mTypeForMetaPath);
  
  			aFilters.push(sFilter);
  			return sFilter;
  		}
docs: Adds the filter for the given element to the array of filters.
  
  @param {object} oFilterElement The element for which a filter is computed
  @returns {string} The filter for the given element; <code>undefined</code> if a key
  property for the element is missing.