community[patch]: fix CometTracer bug (#20796)

Hi! My name is Alex, I'm an SDK engineer from
[Comet](https://www.comet.com/site/)

This PR updates the `CometTracer` class.

Fixed an issue when `CometTracer` failed while logging the data to Comet
because this data is not JSON-encodable.

The problem was in some of the `Run` attributes that could contain
non-default types inside, now these attributes are taken not from the
run instance, but from the `run.dict()` return value.

libs/community/langchain_community/callbacks/tracers/comet.py

@@ -70,24 +70,26 @@ class CometTracer(BaseTracer):
         self._flush: Callable[[], None] = comet_llm_api.flush
 
     def _persist_run(self, run: "Run") -> None:
+        run_dict: Dict[str, Any] = run.dict()
         chain_ = self._chains_map[run.id]
-        chain_.set_outputs(outputs=run.outputs)
+        chain_.set_outputs(outputs=run_dict["outputs"])
         self._chain_api.log_chain(chain_)
 
     def _process_start_trace(self, run: "Run") -> None:
+        run_dict: Dict[str, Any] = run.dict()
         if not run.parent_run_id:
             # This is the first run, which maps to a chain
             chain_: "Chain" = self._chain.Chain(
-                inputs=run.inputs,
+                inputs=run_dict["inputs"],
                 metadata=None,
                 experiment_info=self._experiment_info.get(),
             )
             self._chains_map[run.id] = chain_
         else:
             span: "Span" = self._span.Span(
-                inputs=run.inputs,
+                inputs=run_dict["inputs"],
                 category=_get_run_type(run),
-                metadata=run.extra,
+                metadata=run_dict["extra"],
                 name=run.name,
             )
             span.__api__start__(self._chains_map[run.parent_run_id])
@@ -95,12 +97,13 @@ class CometTracer(BaseTracer):
             self._span_map[run.id] = span
 
     def _process_end_trace(self, run: "Run") -> None:
+        run_dict: Dict[str, Any] = run.dict()
         if not run.parent_run_id:
             pass
             # Langchain will call _persist_run for us
         else:
             span = self._span_map[run.id]
-            span.set_outputs(outputs=run.outputs)
+            span.set_outputs(outputs=run_dict["outputs"])
             span.__api__end__()
 
     def flush(self) -> None: