Can't redirect output of _stash()

[tringcooler]

[tmp]$ cat > t1.py
_stash('echo here')

[tmp]$ t1
here
[tmp]$ t1 > &3
here
[tmp]$ t1 | echo sss
here
sss
[tmp]$ 

When use _stash() to invoke commands, its output is always write to _stash.io, and _stash.io can not be redirected.