Move TrialResult import in langchain to TYPE_CHECKING only

Signed-off-by: Anuradha Karuppiah <26330987+AnuradhaKaruppiah@users.noreply.github.com>

Author: AnuradhaKaruppiah

packages/nvidia_nat_langchain/src/nat/plugins/langchain/langsmith/langsmith_optimization_callback.py

@@ -15,12 +15,11 @@
 
 import logging
 import re
+from typing import TYPE_CHECKING
 from typing import Any
 
 import langsmith
 
-from nat.profiler.parameter_optimization.optimizer_callbacks import TrialResult
-
 from .langsmith_evaluation_callback import _LS_RETRY_DELAY_S
 from .langsmith_evaluation_callback import _backfill_feedback_for_unlinked_items
 from .langsmith_evaluation_callback import _eager_link_run_to_item
@@ -32,6 +31,9 @@
 
 logger = logging.getLogger(__name__)
 
+if TYPE_CHECKING:
+    from nat.profiler.parameter_optimization.optimizer_callbacks import TrialResult
+
 
 class LangSmithOptimizationCallback:
     """Per-trial experiment projects with OTEL trace linking and prompt management.