class HTTP::Options

def features=(features)
  @features = features.each_with_object({}) do |(name, opts_or_feature), h|
    h[name] = if opts_or_feature.is_a?(Feature)
                opts_or_feature
              else
                unless (feature = self.class.available_features[name])
                  argument_error! "Unsupported feature: #{name}"
                end
                feature.new(**opts_or_feature)
              end
  end
end