orm.go
func (f *Field) FilterAttrTopN(n uint64, row *PQLRowQuery, attrName string, attrValues ...interface{}) *PQLRowQuery {
	return f.filterAttrTopN(n, row, attrName, attrValues...)
}
func (f *Field) FilterAttrTopN(n uint64, row *PQLRowQuery, attrName string, attrValues ...interface{}) *PQLRowQuery {
	return f.filterAttrTopN(n, row, attrName, attrValues...)
}
// FilterAttrTopN creates a TopN query with the given item count, row, attribute name and filter values for that field
// The attrName and attrValues arguments work together to only return Rows which have the attribute specified by attrName with one of the values specified in attrValues.