# File lib/rack/content_type.rb, line 18
    def call(env)
      status, headers, body = @app.call(env)
      headers = Utils::HeaderHash.new(headers)

      unless STATUS_WITH_NO_ENTITY_BODY.include?(status)
        headers[CONTENT_TYPE] ||= @content_type
      end

      [status, headers, body]
    end