How to specfy the terminal of USB 6210 with python ?

Dear all,

I am learning how to use the nidaq device with python.

we have USB 6210 and python module nidaqmx.

we want to use USB 6210 as counter.

i made python code below.
###################################

import nidaqmx

counter = nidaqmx.Task()

rate = 100000

co1 = counter.co_channels.add_co_pulse_chan_freq(

           counter = "Dev2/ctr0",

           units = FrequencyUnits.HZ,

           freq = rate)

# if terminal is selected, daq is not working.

co1.co_pulse_term = "Dev2/PFI7"

counter.start()

######################################

when terminal is not selected, counter is output from PFI4.

please help me if you know how to select.

actually, i made program for checking the bhavior this problem.

###################################

import nidaqmx

counter = nidaqmx.Task()

rate = 100000

co1 = counter.co_channels.add_co_pulse_chan_freq(

           counter = "Dev2/ctr0",

           units = FrequencyUnits.HZ,

           freq = rate)

counter.start()

with nidaqmx.Task() as counter1:

      rate = 50000

      co1 = counter1.co_channels.add_co_pulse_chan_freq(

      counter = "Dev2/ctr0",

      freq = rate)

      co1.co_pulse_term = "Dev2/PFI7"

      counter1.start()

      h = input("ok ? >>")

######################################

In this case, i can select terminal in next task.

if i write terminal in frist task, error is shown.

please help me if you have solution.

best regards