Add OpenLLM wrapper(#6578)

LLM wrapper for models served with OpenLLM

---------

Signed-off-by: Aaron <29749331+aarnphm@users.noreply.github.com>
Authored-by: Aaron Pham <29749331+aarnphm@users.noreply.github.com>
Co-authored-by: Chaoyu <paranoyang@gmail.com>

docs/extras/ecosystem/integrations/openllm.mdx

@@ -0,0 +1,70 @@
+# OpenLLM
+
+This page demonstrates how to use [OpenLLM](https://github.com/bentoml/OpenLLM)
+with LangChain.
+
+`OpenLLM` is an open platform for operating large language models (LLMs) in
+production. It enables developers to easily run inference with any open-source
+LLMs, deploy to the cloud or on-premises, and build powerful AI apps.
+
+## Installation and Setup
+
+Install the OpenLLM package via PyPI:
+
+```bash
+pip install openllm
+```
+
+## LLM
+
+OpenLLM supports a wide range of open-source LLMs as well as serving users' own
+fine-tuned LLMs. Use `openllm model` command to see all available models that
+are pre-optimized for OpenLLM.
+
+## Wrappers
+
+There is a OpenLLM Wrapper which supports loading LLM in-process or accessing a
+remote OpenLLM server:
+
+```python
+from langchain.llms import OpenLLM
+```
+
+### Wrapper for OpenLLM server
+
+This wrapper supports connecting to an OpenLLM server via HTTP or gRPC. The
+OpenLLM server can run either locally or on the cloud.
+
+To try it out locally, start an OpenLLM server:
+
+```bash
+openllm start flan-t5
+```
+
+Wrapper usage:
+
+```python
+from langchain.llms import OpenLLM
+
+llm = OpenLLM(server_url='http://localhost:3000')
+
+llm("What is the difference between a duck and a goose? And why there are so many Goose in Canada?")
+```
+
+### Wrapper for Local Inference
+
+You can also use the OpenLLM wrapper to load LLM in current Python process for
+running inference.
+
+```python
+from langchain.llms import OpenLLM
+
+llm = OpenLLM(model_name="dolly-v2", model_id='databricks/dolly-v2-7b')
+
+llm("What is the difference between a duck and a goose? And why there are so many Goose in Canada?")
+```
+
+### Usage
+
+For a more detailed walkthrough of the OpenLLM Wrapper, see the
+[example notebook](../modules/models/llms/integrations/openllm.ipynb)