pub unsafe extern "C" fn rocksdb_optimistictransaction_begin(
otxn_db: *mut rocksdb_optimistictransactiondb_t,
write_options: *const rocksdb_writeoptions_t,
otxn_options: *const rocksdb_optimistictransaction_options_t,
old_txn: *mut rocksdb_transaction_t
) -> *mut rocksdb_transaction_t