Description of issue
In the documentation for niFgen.Session the parameter channel_name is listed as having a default value of 'None':

Further down in the documentation, channel_name is listed as having a default value of '0':

My understanding is that these are two different things -- on a two-channel device, a default value of '0' would indicate a session contained only channel 0, whereas a value of None would indicate it contained all channels (same as leaving the terminal unwired or wired to a blank string in LabVIEW).