Pass iframe through sanitize

Hello,
I want to let users place in textfield an iframe tag from google maps.
Sanitize cuts everything. I want to add some kind of rule to sanitize,
so
it cuts js, but pass through an iframe from google maps and yandex maps
Tried to place in config config.action_view.sanitized_allowed_tags =
%w(‘iframe’) . It didn’t help.
sample

In config/initializers/sanitizer.rb

add:

HTML::WhiteListSanitizer.allowed_tags << ‘iframe’