code: static void addQueryParams(Set<Entry<String, Object>> entrySet, StringBuilder buf) {
      // (similar to UrlEncodedContent)
      boolean first = true;
      for (Map.Entry<String, Object> nameValueEntry : entrySet) {
        Object value = nameValueEntry.getValue();
        if (value != null) {
          String name = CharEscapers.escapeUriQuery(nameValueEntry.getKey());
          if (value instanceof Collection<?>) {
            Collection<?> collectionValue = (Collection<?>) value;
            for (Object repeatedValue : collectionValue) {
              first = appendParam(first, buf, name, repeatedValue);
            }
          } else {
            first = appendParam(first, buf, name, value);
          }
        }
      }
    }
docs: Adds query parameters from the provided entrySet into the buffer.