What is a message hash in bitcoin transaction ? Z ?

[COBRAS]

I try, but I get error code,

assert self.vk.verify_digest(binascii.unhexlify(r + s), binascii.
unhexlify(h))                                                       
  File "/usr/local/lib/python3.8/dist-packages/ecdsa/keys.py", line 7
36, in verify_digest                                                 
    raise BadSignatureError("Signature verification failed")         
ecdsa.keys.BadSignatureError: Signature verification failed