'SecurityOptions.allowInstances(klass, klass, ...): allow instances
of the specified classes
This will also allow the \'instance\', \'class\' (renamed \'classobj\' in
Python 2.3), and \'module\' types, as well as basic types.'

def allowInstancesOf(self, *classes):

    self.allowBasicTypes()
    self.allowTypes('instance', 'class', 'classobj', 'module')
    for klass in classes:
        self.allowTypes(qual(klass))
        self.allowModules(klass.__module__)
        self.allowedClasses[klass] = 1
