You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: preview.rb
    path of file: ./repos/stackneveroverflow/vendor/bundle/ruby/2.3.0/gems/actionmailer-5.0.3/lib/action_mailer
    
    the code of the file until where you have to start completion: require 'active_support/descendants_tracker'

module ActionMailer
  module Previews #:nodoc:
    extend ActiveSupport::Concern

 
    
      def register_preview_interceptor(interceptor)
        preview_interceptor = case interceptor
          when String, Symbol
            interceptor.to_s.camelize.constantize
          else
            interceptor
          end