#NEWLINE# def __init__( self , callback , callback_time , io_loop = None ) : #NEWLINE# #INDENT# self . callback = callback_time #NEWLINE# if ( callback_time <= 0 ) : #NEWLINE# #INDENT# raise ValueError ( 'Periodic callback must have a positive callback_time' ) #NEWLINE# #UNINDENT# self . callback_time = callback_time #NEWLINE# self . io_loop = ( io_loop or IOLoop . current ( ) ) #NEWLINE# self . _running = False #NEWLINE# self . _timeout = None