Update PromptLayerOpenAI LLM to include support for ASYNC API (#1066)

This PR updates `PromptLayerOpenAI` to now support requests using the
[Async
API](https://langchain.readthedocs.io/en/latest/modules/llms/async_llm.html)
It also updates the documentation on Async API to let users know that
PromptLayerOpenAI also supports this.

`PromptLayerOpenAI` now redefines `_agenerate` a similar was to how it
redefines `_generate`

docs/modules/llms/async_llm.ipynb

@@ -1,6 +1,7 @@
 {
  "cells": [
   {
+   "attachments": {},
    "cell_type": "markdown",
    "id": "f6574496-b360-4ffa-9523-7fd34a590164",
    "metadata": {},
@@ -9,7 +10,7 @@
     "\n",
     "LangChain provides async support for LLMs by leveraging the [asyncio](https://docs.python.org/3/library/asyncio.html) library.\n",
     "\n",
-    "Async support is particularly useful for calling multiple LLMs concurrently, as these calls are network-bound. Currently, only `OpenAI` is supported, but async support for other LLMs is on the roadmap.\n",
+    "Async support is particularly useful for calling multiple LLMs concurrently, as these calls are network-bound. Currently, only `OpenAI` and `PromptLayerOpenAI` is supported, but async support for other LLMs is on the roadmap.\n",
     "\n",
     "You can use the `agenerate` method to call an OpenAI LLM asynchronously."
    ]

langchain/llms/promptlayer_openai.py

@@ -53,3 +53,27 @@ class PromptLayerOpenAI(OpenAI, BaseModel):
                 get_api_key(),
             )
         return generated_responses
+
+    async def _agenerate(
+        self, prompts: List[str], stop: Optional[List[str]] = None
+    ) -> LLMResult:
+        from promptlayer.utils import get_api_key, promptlayer_api_request
+
+        request_start_time = datetime.datetime.now().timestamp()
+        generated_responses = await super()._agenerate(prompts, stop)
+        request_end_time = datetime.datetime.now().timestamp()
+        for i in range(len(prompts)):
+            prompt = prompts[i]
+            resp = generated_responses.generations[i]
+            promptlayer_api_request(
+                "langchain.PromptLayerOpenAI.async",
+                "langchain",
+                [prompt],
+                self._identifying_params,
+                self.pl_tags,
+                resp[0].text,
+                request_start_time,
+                request_end_time,
+                get_api_key(),
+            )
+        return generated_responses