langchain_anthropic[patch]: Invoke callback prior to yielding token (#18274)

## PR title
langchain_anthropic[patch]: Invoke callback prior to yielding

## PR message
- Description: Invoke callback prior to yielding token in _stream and
_astream methods for anthropic.
- Issue: https://github.com/langchain-ai/langchain/issues/16913
- Dependencies: None
- Twitter handle: None

libs/partners/anthropic/langchain_anthropic/llms.py

@@ -300,9 +300,10 @@ class AnthropicLLM(LLM, _AnthropicCommon):
             prompt=self._wrap_prompt(prompt), stop_sequences=stop, stream=True, **params
         ):
             chunk = GenerationChunk(text=token.completion)
-            yield chunk
+
             if run_manager:
                 run_manager.on_llm_new_token(chunk.text, chunk=chunk)
+            yield chunk
 
     async def _astream(
         self,
@@ -336,9 +337,10 @@ class AnthropicLLM(LLM, _AnthropicCommon):
             **params,
         ):
             chunk = GenerationChunk(text=token.completion)
-            yield chunk
+
             if run_manager:
                 await run_manager.on_llm_new_token(chunk.text, chunk=chunk)
+            yield chunk
 
     def get_num_tokens(self, text: str) -> int:
         """Calculate number of tokens."""