I think one way Python has to write things like regexes is use
r'\x02[)>@O6@PA5931KESTR-1-J-DE-00@1P10795TR@12VALLEGRO@10VUSA-MANCHESTER@20P@9D1832@6D20181115@14D20231114@Z2@Q1500NAR000@20T1@1T1832967HNAA@2TN/A@1Q1500@2Q0@1Z7B2AEC8F0BB7490389517A21118CDB@@\x03'
instead of the u prefix. The r is for raw, and I believe its use is to handle the backslash issue - see the third line/paragraph here.