code: public Body addBody(String language, String body) {
          language = determineLanguage(language);
  
          removeBody(language);
  
          Body messageBody = new Body(language, body);
          addExtension(messageBody);
          return messageBody;
      }
docs: Adds a body with a corresponding language.
  
  @param language the language of the body being added.
  @param body the body being added to the message.
  @return the new {@link org.jivesoftware.smack.packet.Message.Body}
  @throws NullPointerException if the body is null, a null pointer exception is thrown
  @since 3.0.2