#NEWLINE# def isValid( self , value ) : #NEWLINE# #INDENT# 'Tests if the given value is valid.\n\n        @param value:\n                   the value to validate.\n        @return: C{True} for valid value, otherwise C{False}.\n        ' #NEWLINE# return ( ( value is None ) if value . _onlyNullAllowed else ( value is not None ) )