instance method content_type

# File actionpack/lib/action_dispatch/http/response.rb, line 245
    def content_type
      if self.class.return_only_media_type_on_content_type
        ActiveSupport::Deprecation.warn(
          "Rails 6.1 will return Content-Type header without modification." \
          " If you want just the MIME type, please use `#media_type` instead."
        )

        content_type = super
        content_type ? content_type.split(/;\s*charset=/)[0].presence : content_type
      else
        super.presence
      end
    end