Bug - .py file with 2 underscore not recognized by erpnext.utils.map_current_doc

Hello,
I faced this problem
image

when using map_current_doc method. My code in custom script include
erpnext.utils.map_current_doc({
method: “eupapp.eupapp.doctype.don_dat_hang.don_dat_hang.populate_items”,

Just change the .py name from “don_dat_hang” to “dat_hang” and change the custom script accordingly fixed the problem (after hours of debuging).
Is this a bug?