variant=

# File actionpack/lib/action_dispatch/http/mime_negotiation.rb, line 87
      def variant=(variant)
        variant = Array(variant)

        if variant.all? { |v| v.is_a?(Symbol) }
          @variant = ActiveSupport::ArrayInquirer.new(variant)
        else
          raise ArgumentError, "request.variant must be set to a Symbol or an Array of Symbols. "              "For security reasons, never directly set the variant to a user-provided value, "              "like params[:variant].to_sym. Check user-provided value against a whitelist first, "              "then set the variant: request.variant = :tablet if params[:variant] == 'tablet'"
        end
      end