fix: qualify HASH_PATTERN reference in RenderBuffer._ensure_hash (fixes #692) (#694)

Co-authored-by: apoorv-narayanam <nvcapoorv1234@gmail.com>

Author: apoorv-narayanam

preswald/engine/utils.py

@@ -1,12 +1,13 @@
+import hashlib
 import json
 import logging
+import re
 import zlib
 from datetime import date, datetime
-from typing import Any, Dict, List, Union
-import hashlib
+from typing import Any
+
 import msgpack
 import numpy as np
-import re
 
 
 logger = logging.getLogger(__name__)
@@ -198,7 +199,7 @@ class RenderBuffer:
     HASH_PATTERN = re.compile(r"^[0-9a-f]{64}$")
 
     def __init__(self):
-        self._state_cache: Dict[str, str] = {}
+        self._state_cache: dict[str, str] = {}
 
     def has_changed(self, component_id: str, new_value: Any) -> bool:
         """Check if the new hash differs from the cached one."""
@@ -223,7 +224,7 @@ def should_render(self, component_id: str, new_value: Any) -> bool:
 
     def _ensure_hash(self, value: Any) -> str:
         """Convert value to SHA256 hash. Accepts either a hash string or a hashable object."""
-        if isinstance(value, str) and HASH_PATTERN.match(value):
+        if isinstance(value, str) and self.HASH_PATTERN.match(value):
             return value  # already a hash
         try:
             cleaned = clean_nan_values(value)