[pyngl-talk] how can I change the tickmark of the contour_map

[cgc at mail.ustc.edu.cn]

hello everyone
I want to know how to change the tick mark of the output at the using contour_map condition.
for example :
 
on this output, the program set the tick mark automatic ,i want to change the 30N 15N 0 15S 30S to 40N,20N,0 20S 40S, but i can't find a useful way. tmYLlabelValue can't work.
so can you help me?
thanks
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