generate a secret key for python code example

Example: python generate secret key

>>> import secrets
>>> secrets.token_bytes(16)
b'\xebr\x17D*t\xae\xd4\xe3S\xb6\xe2\xebP1\x8b'
>>> secrets.token_hex(16)
'f9bf78b9a18ce6d46a0cd2b0b86df9da'
>>> token_urlsafe(16)  
'Drmhze6EPcv0fN_81Bj-nA'