def __init__(self, log_dir, app_name, bigdl_type="<STR_LIT:float>"):
JavaValue.__init__(self, None, bigdl_type, log_dir, app_name)<EOL>
Create a TrainSummary. Logs will be saved to log_dir/app_name/train.


:param log_dir: the root dir to store the logs
:param app_name: the application name