incompatibility with latest pyserial 3.5

[nicop]

Great work you did with this package. I come from gammu package which is unreliable to receive incoming SMS.

Just a problem I recently encountered:
I have updated pyserial from 3.4 to 3.5 and when I run my SMS incoming program handler using gsmmodem I get a message which state that 'serial' does not have 'Serial' attribute, at the latest call:
super(GsmModem, self).connect() in modem.py

I don't have the exact error message anymore since I got back to pyserial 3.4 which runs perfectly with gsmmodem as before.
I can downgrade to 3.4 and send it to you if needed.

platform : Raspberry Pi Zero 2W
Python : 3.9.2
OS : Rasp OS Buster 32 bit
modem : Huawei E3531