avoid duplicate say in function call example (#1317)

examples/voice-pipeline-agent/function_calling_weather.py

@@ -39,18 +39,25 @@ async def get_weather(
         # that it might take awhile:
         # Option 1: you can use .say filler message immediately after the call is triggered
         # Option 2: you can prompt the agent to return a text response when it's making a function call
-        call_ctx = AgentCallContext.get_current()
-        filler_messages = [
-            "Let me check the weather in {location} for you.",
-            "Let me see what the weather is like in {location} right now.",
-            # LLM will complete this sentence if it is added to the end of the chat context
-            "The current weather in {location} is ",
-        ]
-        message = random.choice(filler_messages).format(location=location)
-
-        # NOTE: set add_to_chat_ctx=True will add the message to the end
-        #   of the chat context of the function call for answer synthesis
-        speech_handle = await call_ctx.agent.say(message, add_to_chat_ctx=True)  # noqa: F841
+        agent = AgentCallContext.get_current().agent
+
+        if (
+            not agent.chat_ctx.messages
+            or agent.chat_ctx.messages[-1].role != "assistant"
+        ):
+            # skip if assistant already said something
+            filler_messages = [
+                "Let me check the weather in {location} for you.",
+                "Let me see what the weather is like in {location} right now.",
+                # LLM will complete this sentence if it is added to the end of the chat context
+                "The current weather in {location} is ",
+            ]
+            message = random.choice(filler_messages).format(location=location)
+            logger.info(f"saying filler message: {message}")
+
+            # NOTE: set add_to_chat_ctx=True will add the message to the end
+            #   of the chat context of the function call for answer synthesis
+            speech_handle = await agent.say(message, add_to_chat_ctx=True)  # noqa: F841
 
         logger.info(f"getting weather for {location}")
         url = f"https://wttr.in/{urllib.parse.quote(location)}?format=%C+%t"