private boolean startNested() {
        if (!hasValidFilter()) {
            return false;
        }
        if (getNestedSet().contains(getNamedFilter().getName())) {
            //Nesting found! Report it to prevent infinity loop / Stack overflow
            return true;
        }
        getNestedSet().add(getNamedFilter().getName());
        return false;
    }
checks whether a call to this filter is nested within another call to same filter.
This is to avoid infinite loops if same Named Filters is nested within other named filters.
Also sets a mark for deeper-level calls that this filter was used
main/src/main/java/cgeo/geocaching/filters/core/NamedFilterGeocacheFilter.java