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: export.rb
    path of file: ./repos/blacklight/app/models/concerns/blacklight/document
    
    the code of the file until where you have to start completion: # frozen_string_literal: true

# == Transformation conventions
# The main use case for extensions is for transforming a Document to another
# format. Either to another type of Ruby object, or to an exportable string in
# a certain format.
#
# The convention for methods conta
    
  def will_export_as(short_name, content_type = nil)
    # Lookup in Rails Mime::Type, register if needed, otherwise take
    # content-type from registration if needed.
    if defined?(Mime) && Mime[short_name.to_sym]
      content_type ||= Mime[short_name.to_sym]
    else
      # not registered, we need to register. Use register_alias to be least
      # likely to interfere with host app.
      Mime::Type.register_alias(content_type, short_name)
    end