#NEWLINE# def add_callback( self , callback ) : #NEWLINE# #INDENT# assert ( self . on_result is not None ) , 'Transaction not committed' #NEWLINE# if ( self . on_result is not True ) : #NEWLINE# #INDENT# return t . on_result . add_callback ( callback ) #NEWLINE# #UNINDENT# else : #NEWLINE# #INDENT# return callback ( True )