def prepare_batch(self):
for cert in self.certificates_to_issue:<EOL><INDENT>self.certificate_handler.validate_certificate(cert)<EOL><DEDENT>self.merkle_tree.populate(self.get_certificate_generator())<EOL>logging.info('<STR_LIT>', b2h(self.merkle_tree.get_blockchain_data()))<EOL>return self.merkle_tree.get_blockchain_data()<EOL>
Propagates exception on failure
:return: byte array to put on the blockchain