code: public CreateUserPoolRequest withUsernameAttributes(UsernameAttributeType... usernameAttributes) {
          java.util.ArrayList<String> usernameAttributesCopy = new java.util.ArrayList<String>(usernameAttributes.length);
          for (UsernameAttributeType value : usernameAttributes) {
              usernameAttributesCopy.add(value.toString());
          }
          if (getUsernameAttributes() == null) {
              setUsernameAttributes(usernameAttributesCopy);
          } else {
              getUsernameAttributes().addAll(usernameAttributesCopy);
          }
          return this;
      }
docs: <p>
  Specifies whether email addresses or phone numbers can be specified as usernames when a user signs up.
  </p>
  
  @param usernameAttributes
  Specifies whether email addresses or phone numbers can be specified as usernames when a user signs up.
  @return Returns a reference to this object so that method calls can be chained together.
  @see UsernameAttributeType