community[patch] : [Fiddler] ensure dataset is not added if model is present (#19293)

**Description:**
- minor PR to speed up onboarding by not trying to add a dataset, if a
model is already present.
- replace batch publish API with streaming when single events are
published.

**Dependencies:** any dependencies required for this change
**Twitter handle:** behalder

Co-authored-by: Barun Halder <barun@fiddler.ai>

libs/community/langchain_community/callbacks/fiddler_callback.py

@@ -131,6 +131,7 @@ class FiddlerCallbackHandler(BaseCallbackHandler):
                 dataset_info.columns[i].data_type = self.fdl.DataType.CATEGORY
                 dataset_info.columns[i].possible_values = [SUCCESS, FAILURE]
 
+        if self.model not in self.fiddler_client.get_model_names(self.project):
             if self.model not in self.fiddler_client.get_dataset_names(self.project):
                 print(  # noqa: T201
                     f"adding dataset {self.model} to project {self.project}."
@@ -166,8 +167,6 @@ class FiddlerCallbackHandler(BaseCallbackHandler):
                 ],
                 custom_features=self.custom_features,
             )
-
-        if self.model not in self.fiddler_client.get_model_names(self.project):
             print(  # noqa: T201
                 f"adding model {self.model} to project {self.project}."
                 "This only has to be done once."  # noqa: T201
@@ -286,7 +285,13 @@ class FiddlerCallbackHandler(BaseCallbackHandler):
                 df[key] = [value] * prompt_count if isinstance(value, int) else value
 
         try:
+            if df.shape[0] > 1:
                 self.fiddler_client.publish_events_batch(self.project, self.model, df)
+            else:
+                df_dict = df.to_dict(orient="records")
+                self.fiddler_client.publish_event(
+                    self.project, self.model, event=df_dict[0]
+                )
         except Exception as e:
             print(  # noqa: T201
                 f"Error publishing events to fiddler: {e}. continuing..."