import re
cases = ["test_TEST bfd",
    "test_TEST_TEST_1_TEST_13DAHA bfd",
    "test_TEST_TEST_1_TEST__13DAHA bfd",
    "test__TEST_TEST",
    "test_TEST__DHJF",
    "test_TEST__Ddsa"
]
pattern = re.compile(r'_([0-9A-Z]+(?:_[0-9A-Z]+)*)(?:__[0-9A-Z_]+)?')
for case in cases:
	matches = pattern.findall(case)
	print(matches)