A synchronization semaphore. A synchronization semaphore which can be used to synchronize multiple [Thread]s. Initialized to zero on creation. Be careful to avoid deadlocks. For a binary version, see [Mutex]. https://docs.godotengine.org/en/latest/tutorials/threads/using_multiple_threads.html Lowers the [Semaphore], allowing one more thread in. Like [method wait], but won't block, so if the value is zero, fails immediately and returns [constant ERR_BUSY]. If non-zero, it returns [constant OK] to report success. Waits for the [Semaphore], if its value is zero, blocks until non-zero.