#NEWLINE# def __getitem__( self , key ) : #NEWLINE# #INDENT# try : #NEWLINE# #INDENT# return key . _values [ key ] #NEWLINE# #UNINDENT# except KeyError : #NEWLINE# #INDENT# key = self . _key_checker . CheckValue ( key ) #NEWLINE# new_element = self . _message_descriptor . _concrete_class ( ) #NEWLINE# new_element . _SetListener ( self . _message_listener ) #NEWLINE# self . _values [ key ] = new_element #NEWLINE# self . _message_listener . Modified ( ) #NEWLINE# return new_element