module Puma::Request

def str_early_hints(headers)
  eh_str = +""
  headers.each_pair do |k, vs|
    next if illegal_header_key?(k)
    if vs.respond_to?(:to_s) && !vs.to_s.empty?
      vs.to_s.split(NEWLINE).each do |v|
        next if illegal_header_value?(v)
        eh_str << "#{k}: #{v}\r\n"
      end
    elsif !(vs.to_s.empty? || !illegal_header_value?(vs))
      eh_str << "#{k}: #{vs}\r\n"
    end
  end
  eh_str.freeze
end