docs: Add Python SDK reference page (#773)

* Add Python SDK client.

* Update dependencies for docs group.

docs/docs/cloud/reference/sdk/python_sdk_ref.md

@@ -1,2 +1,79 @@
 # Python SDK Reference
-Coming soon
+
+The Python SDK provides four underlying clients (`AssistantsClient`, `ThreadsClient`, `RunsClient`, `CronClient`) that correspond to each of the core API models and one top-level client (`LangGraphClient`) to access them.
+
+## get_client()
+
+The `get_client()` function returns the top-level `LangGraphClient` client.
+
+```python
+from langgraph_sdk import get_client
+
+# get top-level LangGraphClient
+client = get_client(url="http://localhost:8123")
+
+# example usage: client.<model>.<method_name>()
+assistants = await client.assistants.get(assistant_id="some_uuid")
+```
+
+::: langgraph_sdk.client.get_client
+    handler: python
+
+## LangGraphClient
+
+`LangGraphClient` is the top-level client for accessing `AssistantsClient`, `ThreadsClient`, `RunsClient`, and `CronClient`.
+
+::: langgraph_sdk.client.LangGraphClient
+    handler: python
+
+## AssistantsClient
+
+Access the `AssistantsClient` via the `LangGraphClient.assistants` attribute.
+```python
+from langgraph_sdk import get_client
+
+client = get_client(url="http://localhost:8123")
+await client.assistants.<method_name>()
+```
+
+::: langgraph_sdk.client.AssistantsClient
+    handler: python
+
+## ThreadsClient
+
+Access the `ThreadsClient` via the `LangGraphClient.threads` attribute.
+```python
+from langgraph_sdk import get_client
+
+client = get_client(url="http://localhost:8123")
+await client.threads.<method_name>()
+```
+
+::: langgraph_sdk.client.ThreadsClient
+    handler: python
+
+## RunsClient
+
+Access the `RunsClient` via the `LangGraphClient.runs` attribute.
+```python
+from langgraph_sdk import get_client
+
+client = get_client(url="http://localhost:8123")
+await client.runs.<method_name>()
+```
+
+::: langgraph_sdk.client.RunsClient
+    handler: python
+
+## CronClient
+
+Access the `CronClient` via the `LangGraphClient.crons` attribute.
+```python
+from langgraph_sdk import get_client
+
+client = get_client(url="http://localhost:8123")
+await client.crons.<method_name>()
+```
+
+::: langgraph_sdk.client.CronClient
+    handler: python