MTEncDecModel has no attribute device
**Describe the bug**

I called
MTEncDecModel.restore_from('zh_en_24x6.nemo').cuda('cuda:0')
if I assign the parameter to .cuda() as above, it will raise an error 
'no attribute device'

**Steps/Code to reproduce bug**

as above

A  helpful guide on on how to craft a minimal bug report  http://matthewrocklin.com/blog/work/2018/02/28/minimal-bug-reports. 

**Expected behavior**

as above

**Environment overview (please complete the following information)**

as instructed in the readme, pip install nemo_toolkit['all'], python 3.8 nemo 1.4 pytorch 1.9

**Environment details**

as above

**Additional context**

probably not
