Verifies the signature of the current message.
def verify_signature() -> None: ...
This method attempts to verify the signature of the input message. If the message does not have a certificate attached, the class will attempt to verify the signature using the certificate supplied in signer_cert (if any). If no certificate is found, the class fails with an error.
If this method is successful, the signer_cert property will contain the certificate information of the message signer.
NOTE: This function does not attempt to check the validity of the signing certificate itself.