code: function findWriteStream(arg, copy) {
    if (copy.proto !== 'ReadableState') return null
    if (copy.pipes != null && copy.pipes.proto !== 'WriteStream') return null
    return arg.pipes
  }
docs: The WriteStream is attached to the pipes of a ReadableState
  of the ReadStream that is piped into it.
  
  If one is found, it is returned so it can be added to the copied args.
  
  @name findWriteStream
  @function
  @private
  @param {Object} arg the original arg found on the resource
  @param {Object} copy the clone of the arg