docs: private RequestTemplate appendQuery(String name,
                                        Iterable<String> values,
                                        CollectionFormat collectionFormat) {
      if (!values.iterator().hasNext()) {
        /* empty value, clear the existing values */
        this.queries.remove(name);
        return this;
      }
  
      /* create a new query template out of the information here */
      this.queries.compute(name, (key, queryTemplate) -> {
        if (queryTemplate == null) {
          return QueryTemplate.create(name, values, this.charset, collectionFormat);
        } else {
          return QueryTemplate.append(queryTemplate, values, collectionFormat);
        }
      });
      return this;
    }