to_json o@((key,value):kvs) | is_non_empty_string key = Object [(key,to_json value) | (key, value) <- o]
to_json o@((key,value):kvs) | is_non_empty_string key = Object [(key,to_json value) | (key, value) <- o]
to_json o@((key,value):kvs) | is_non_empty_string key = Object [(key,to_json value) | (key, value) <- o]