Implement an in-memory key–record database that supports basic CRUD on fields plus an exclusive lock per record. You are given a sequence of queries. Each query is an array of strings. Implement a function that processes all queries in order and returns an array of strings containing the outputs of the queries that produce output. ### Data model - The database contains **records** identified by `recordKey` (string). - Each record is a map from `field` (string) to `value` (string). ### Locking model - A record can be **unlocked** or **locked by exactly one user** (`userId`, string). - A lock applies to the whole record (all its fields). - **Reads are always allowed**. - **Writes/deletes are allowed only if** the record is not locked, or it is locked by the same `userId` performing the operation. ### Query types Each query is one of: 1) `SET recordKey field value userId` - If the write is allowed, set `recordKey[field] = value` (creating the record if needed) and output `"OK"`. - Otherwise output `"LOCKED"` and do not change the database. 2) `GET recordKey field` - Output the value if present, otherwise output an empty string `""`. 3) `DELETE recordKey field userId` - If the delete is allowed and the field existed, remove it and output `"true"`. - If the delete is allowed but the field did not exist, output `"false"`. - If the delete is not allowed due to locking, output `"LOCKED"`. - If a record becomes empty after deletion, remove the record entirely. If the record is removed, its lock (if any) is also removed. 4) `LOCK recordKey userId` - If the record does not exist, output `"INVALID"`. - If the record is unlocked, lock it for `userId` and output `"ACQUIRED"`. - If the record is already locked by `userId`, output `"ACQUIRED"` (idempotent). - If the record is locked by a different user, output `"WAIT"`. 5) `UNLOCK recordKey userId` - If the record does not exist, output `"INVALID"`. - If the record is locked by `userId`, unlock it and output `"RELEASED"`. - If the record is unlocked, output `"RELEASED"` (idempotent). - If the record is locked by a different user, output `"INVALID"`. ### Requirements - Process queries efficiently (aim for average O(1) per query using hash maps). - Return outputs **only** for the queries above (all of them produce output in this spec). ### Example If a record `A` is locked by user `u1`, then `SET A x 5 u2` must output `"LOCKED"`, while `GET A x` still returns the stored value (or empty string if missing).