public <T> LazyDataModel<T> getLazyDataModel() {
        if (isLazy()) {
            DataModel<T> value = getDataModel();
            if (value instanceof LazyDataModel) {
                return (LazyDataModel<T>) value;
            }
        }
        return null;
    }
Recalculates filteredValue after adding, updating or removing rows to/from a filtered DataTable.
NOTE: this is only supported for non-lazy DataTables, eg bound to a java.util.List.
primefaces/src/main/java/org/primefaces/component/datatable/DataTable.java