docs: public UrlStringBuilder addParameters(String namespace, Map<String, List<String>> parameters) {
          for (final String name : parameters.keySet()) {
              Validate.notNull(name, "parameter map cannot contain any null keys");
          }
  
          for (final Map.Entry<String, List<String>> newParamEntry : parameters.entrySet()) {
              final String name = newParamEntry.getKey();
              final List<String> values = this.copy(newParamEntry.getValue());
  
              this.parameters.put(namespace + name, values);
          }
          return this;
      }