#NEWLINE# def _PageIndexOperation( self , closure ) : #NEWLINE# #INDENT# ' A private method which will run the given closure if there\n        is a valid index for this page.\n\n        ' #NEWLINE# parent = self . GetParent ( ) #NEWLINE# if parent : #NEWLINE# #INDENT# index = parent . GetPageIndex ( self ) #NEWLINE# if ( index != ( - 1 ) ) : #NEWLINE# #INDENT# closure ( parent , index )