code: public static Map<String, List<String>> extractParametersFromQueryString(String queryString) {
      if (queryString == null) {
        return emptyMap();
      }
  
      // If there is no ? character at the front of the string, append it.
      return extractParametersFromUrl(
        format("restfb://url%s", queryString.startsWith("?") ? queryString : "?" + queryString));
    }
docs: For the given {@code queryString}, extract a mapping of query string parameter names to values.
  <p>
  Example of a {@code queryString} is {@code accessToken=123&expires=345}.
  
  @param queryString
  The URL query string from which parameters are extracted.
  @return A mapping of query string parameter names to values. If {@code queryString} is {@code null}, an empty
  {@code Map} is returned.
  @throws IllegalStateException
  If unable to URL-decode because the JVM doesn't support {@link StandardCharsets#UTF_8}.