fix(typing): resolve ty diagnostics in logging and metrics modules

- logging/buffer/functions.py: add guard clause for None values from dict.get() before comparison
- metrics/base.py: add cast for functools.wraps union type, add set_default_dimensions stub to base class

Resolves 3 of 10 diagnostics from #7929

Author: ConnorKirk

aws_lambda_powertools/logging/buffer/functions.py

@@ -121,6 +121,9 @@ def _check_minimum_buffer_log_level(buffer_log_level, current_log_level):
     buffer_level_num = log_levels.get(buffer_log_level.upper())
     current_level_num = log_levels.get(current_log_level.upper())
 
+    if buffer_level_num is None or current_level_num is None:
+        return False
+
     # Compare numeric levels
     if buffer_level_num < current_level_num:
         return True

aws_lambda_powertools/metrics/base.py

@@ -15,7 +15,7 @@
 import warnings
 from collections import defaultdict
 from contextlib import contextmanager
-from typing import TYPE_CHECKING, Any
+from typing import TYPE_CHECKING, Any, cast
 
 from aws_lambda_powertools.metrics.exceptions import (
     MetricResolutionError,
@@ -375,6 +375,10 @@ def flush_metrics(self, raise_on_empty_metrics: bool = False) -> None:
             print(json.dumps(metrics, separators=(",", ":")))
             self.clear_metrics()
 
+    def set_default_dimensions(self, **dimensions: str) -> None:
+        """Persist dimensions across Lambda invocations. Override in subclass."""
+        pass
+
     def log_metrics(
         self,
         lambda_handler: Callable[[dict, Any], Any] | Callable[[dict, Any, dict | None], Any] | None = None,
@@ -428,7 +432,7 @@ def handler(event, context):
                 default_dimensions=default_dimensions,
             )
 
-        @functools.wraps(lambda_handler)
+        @functools.wraps(cast("Callable[..., Any]", lambda_handler))
         def decorate(event, context, *args, **kwargs):
             unwrapped_context = context.lambda_context if is_durable_context(context) else context
             try: