core/play/src/main/java/play/i18n/MessagesImpl.java
public String at(List<String> keys, Object... args) {
    return messagesApi.get(lang, keys, args);
  }
public String at(List<String> keys, Object... args) {
    return messagesApi.get(lang, keys, args);
  }
Get the message at the first defined key.

<p>Uses `java.text.MessageFormat` internally to format the message.

@param keys the messages keys
@param args the message arguments
@return the formatted message or a default rendering if the key wasn't defined