{
  "context": "This criteria evaluates the engineer's ability to use asyncstdlib's cached_property decorator with lock synchronization to implement thread-safe cached async properties. The focus is on proper use of the caching mechanism, synchronization locks, and cache invalidation.",
  "type": "weighted_checklist",
  "checklist": [
    {
      "name": "Uses cached_property decorator",
      "description": "The engineer imports and uses asyncstdlib.functools.cached_property (or asyncstdlib.cached_property) as a decorator on the mean, variance, and std_dev methods.",
      "max_score": 30
    },
    {
      "name": "Implements lock synchronization",
      "description": "The engineer passes a lock type (such as asyncio.Lock) to the cached_property decorator to enable synchronized concurrent access, preventing multiple simultaneous computations of the same property.",
      "max_score": 30
    },
    {
      "name": "Correct decorator usage",
      "description": "The cached_property decorator is correctly applied to all three async methods (mean, variance, std_dev), transforming them from methods into cached properties that can be accessed as attributes.",
      "max_score": 20
    },
    {
      "name": "Cache invalidation support",
      "description": "The implementation supports cache invalidation through the del statement (e.g., del instance.mean), which is automatically supported by cached_property when used correctly.",
      "max_score": 10
    },
    {
      "name": "Async delay simulation",
      "description": "Each property computation includes an async delay (using asyncio.sleep or equivalent) to simulate an expensive operation as specified in the requirements.",
      "max_score": 10
    }
  ]
}