The user can be informed about anything strange happened during the execution of the node with this method. This will not cancel execution but set a warning icon with the provided message as the tooltip.

Example #1:

  if (m_includedColumns.getIncludeList() == null       || m_includedColumns.getIncludeList().size() <= 0) {      setWarningMessage(          "No columns to transfrom selected. Will have no effect!");  }