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>

tests/integration_tests/llms/test_openllm.py

@@ -0,0 +1,16 @@
+"""Test OpenLLM wrapper."""
+from langchain.llms.openllm import OpenLLM
+
+
+def test_openllm_llm_local() -> None:
+    llm = OpenLLM(model_name="flan-t5", model_id="google/flan-t5-small")
+    output = llm("Say foo:")
+    assert isinstance(output, str)
+
+
+def test_openllm_with_kwargs() -> None:
+    llm = OpenLLM(
+        model_name="flan-t5", model_id="google/flan-t5-small", temperature=0.84
+    )
+    output = llm("Say bar:")
+    assert isinstance(output, str)