formats=

# File actionview/lib/action_view/lookup_context.rb, line 263
    def formats=(values)
      if values
        values = values.dup
        values.concat(default_formats) if values.delete "*/*"
        values.uniq!

        unless Template::Types.valid_symbols?(values)
          invalid_values = values - Template::Types.symbols
          raise ArgumentError, "Invalid formats: #{invalid_values.map(&:inspect).join(", ")}"
        end

        if (values.length == 1) && (values[0] == :js)
          values << :html
          @html_fallback_for_js = true
        end
      end
      super(values)
    end