#NEWLINE# def add( self ) : #NEWLINE# #INDENT# 'A non thread-safe method.' #NEWLINE# next = ( self . index + 1 ) #NEWLINE# if ( next != ( self . index + 1 ) ) : #NEWLINE# #INDENT# self . problem = 1 #NEWLINE# raise ValueError #NEWLINE# #UNINDENT# self . index = next