func (t *BTTracer) SetPipes(stdin io.Reader, stderr io.Writer) {
	t.m.Lock()
	defer t.m.Unlock()

	t.p.stdin = stdin
	t.p.stderr = stderr
}
func (t *BTTracer) SetPipes(stdin io.Reader, stderr io.Writer) {
	t.m.Lock()
	defer t.m.Unlock()

	t.p.stdin = stdin
	t.p.stderr = stderr
}
// Sets the input and output pipes for the tracer.
// Stdout is not redirected; it is instead passed to the
// tracer's Put command.