code: public EntityBuilder addProperties(Map<String, Object> properties) {
      	if(MapUtils.isEmpty(properties)) {
      		throw new IllegalArgumentException("properties cannot be null or empty.");
      	}
          for (String key : properties.keySet()) {
              addProperty(key, properties.get(key));
          }
          return this;
      }
docs: Adds a map of properties to the entity to be built.
  Properties are optional according to the Siren specification.
  @param properties cannot be <code>null</code>.
  @return <code>this</code> builder, never <code>null</code>.