community: adding langchain-predictionguard partner package documentation (#28832)

- *[x] **PR title**: "community: adding langchain-predictionguard
partner package documentation"

- *[x] **PR message**:
- **Description:** This PR adds documentation for the
langchain-predictionguard package to main langchain repo, along with
deprecating current Prediction Guard LLMs package. The LLMs package was
previously broken, so I also updated it one final time to allow it to
continue working from this point onward. . This enables users to chat
with LLMs through the Prediction Guard ecosystem.
    - **Package Links**: 
        -  [PyPI](https://pypi.org/project/langchain-predictionguard/)
- [Github
Repo](https://www.github.com/predictionguard/langchain-predictionguard)
    - **Issue:** None
    - **Dependencies:** None
- **Twitter handle:** [@predictionguard](https://x.com/predictionguard)

- *[x] **Add tests and docs**: All docs have been added for the partner
package, and the current LLMs package test was updated to reflect
changes.


- *[x] **Lint and test**: Linting tests are all passing.

---------

Co-authored-by: ccurme <chester.curme@gmail.com>

libs/community/tests/integration_tests/llms/test_predictionguard.py

@@ -1,10 +1,28 @@
 """Test Prediction Guard API wrapper."""
 
+import pytest
+
 from langchain_community.llms.predictionguard import PredictionGuard
 
 
-def test_predictionguard_call() -> None:
+def test_predictionguard_invoke() -> None:
     """Test valid call to prediction guard."""
-    llm = PredictionGuard(model="OpenAI-text-davinci-003")  # type: ignore[call-arg]
-    output = llm.invoke("Say foo:")
+    llm = PredictionGuard(model="Hermes-3-Llama-3.1-8B")  # type: ignore[call-arg]
+    output = llm.invoke("Tell a joke.")
     assert isinstance(output, str)
+
+
+def test_predictionguard_pii() -> None:
+    llm = PredictionGuard(
+        model="Hermes-3-Llama-3.1-8B",
+        predictionguard_input={"pii": "block"},
+        max_tokens=100,
+        temperature=1.0,
+    )
+
+    messages = [
+        "Hello, my name is John Doe and my SSN is 111-22-3333",
+    ]
+
+    with pytest.raises(ValueError, match=r"Could not make prediction. pii detected"):
+        llm.invoke(messages)