Missing coma in string representation of ModbusPDU

[MrWaloo]

Current output of

print(f"{anyFunctionInstance}")

is (for example):

ReadHoldingRegistersRequest(dev_id=1, transaction_id=0, address=12503, count=7, bits=[], registers=[], status=1retries=0)

A coma is missing between status and retries, it should be:

ReadHoldingRegistersRequest(dev_id=1, transaction_id=0, address=12503, count=7, bits=[], registers=[], status=1, retries=0)

This humble PR corrects it.

[janiversen]

LGTM, thanks