'''How to change log level to print out more message at run time?'''
 . EMAN2's log has four levels: ERROR_LOG, WARNING_LOG, DEBUG_LOG, VARIABLE_LOG. 
 . By default, only the error log will be printed out.
 . This log level can be changed at runtime at Python level.
 . What user need to do to change log level:
 . >>>Log.logger().set_level(Log.LogLevel.WARNING_LOG)