os.environ.get('SSH_ORIGINAL_COMMAND') returns None

[Tzury Bar Yochay]

Trying to follow a technique found at bzr I did the following

added to ~/.ssh/authorized_keys the command="my_parder" parameter
which point to a python script file named 'my_parser' and located in /
usr/local/bin  (file was chmoded as 777)

in that script file '/usr/local/bin/my_parser' I got the following
lines:

#!/usr/bin/env python
import os
print os.environ.get('SSH_ORIGINAL_COMMAND', None)

When trying to ssh e.g. 'ssh localhost'
I get None on the terminal and then the connection is closed.

I wonder if anyone have done such or alike in the past and can help me
with this.
Is there anything I should do in my python file in order to get that
environment variable?