from_session_value

# File actionpack/lib/action_dispatch/middleware/flash.rb, line 115
      def self.from_session_value(value) # :nodoc:
        case value
        when FlashHash # Rails 3.1, 3.2
          flashes = value.instance_variable_get(:@flashes)
          if discard = value.instance_variable_get(:@used)
            flashes.except!(*discard)
          end
          new(flashes, flashes.keys)
        when Hash # Rails 4.0
          flashes = value["flashes"]
          if discard = value["discard"]
            flashes.except!(*discard)
          end
          new(flashes, flashes.keys)
        else
          new
        end
      end