How to inject custom ActionMailer delivery method

I would like to use the Aws::SES::Client api method to send email instead of the smtp settings.

aws-sdk-rails gems allow me to add the custom method on initializer

Aws::Rails.add_action_mailer_delivery_method(:aws_sdk, region: 'us-east-1')

I tried adding a custom method on initilizer like this

 mailer = 'us-east-1', region: 'us-east-1)
 ActionMailer::Base.add_delivery_method(:ses, mailer)

but I got error uninitialized constant ActionMailer (NameError)

Is there anyway to use ses api instead of ses smtp?