class Gem::Net::HTTP::Persistent::Pool

def checkin net_http_args
  if net_http_args.is_a?(Hash) && net_http_args.size == 1 && net_http_args[:force]
    # Bundler::ConnectionPool 2.4+ calls `checkin(force: true)` after fork.
    # When this happens, we should remove all connections from Thread.current
    if stacks = Thread.current[@key]
      stacks.each do |http_args, connections|
        connections.each do |conn|
          @available.push conn, connection_args: http_args
        end
        connections.clear
      end
    end
  else
    stack = Thread.current[@key][net_http_args] ||= []
    raise Bundler::ConnectionPool::Error, 'no connections are checked out' if
      stack.empty?
    conn = stack.pop
    if stack.empty?
      @available.push conn, connection_args: net_http_args
      Thread.current[@key].delete(net_http_args)
      Thread.current[@key] = nil if Thread.current[@key].empty?
    end
  end
  nil
end