code: func NewSignDetachedStream(version Version, detachedsig io.Writer, signer SigningSecretKey) (stream io.WriteCloser, err error) {
  	return newSignDetachedStream(version, detachedsig, signer)
  }
docs: // NewSignDetachedStream creates a stream that consumes plaintext
  // data.  It will write out a detached signature to the io.Writer
  // passed in as detachedsig.