use ssml with litellm vertex

docs/my-website/docs/providers/vertex.md

@@ -1768,7 +1768,7 @@ LiteLLM supports calling [Vertex AI Text to Speech API](https://console.cloud.go
 
 
 
-Usage
+### Usage - Basic
 
 <Tabs>
 <TabItem value="sdk" label="SDK">
@@ -1841,6 +1841,61 @@ print("response from proxy", response)
 </Tabs>
 
 
+### Usage - `ssml` as input
+
+
+<Tabs>
+<TabItem value="sdk" label="SDK">
+
+Vertex AI does not support passing a `model` param - so passing `model=vertex_ai/` is the only required param
+
+**Sync Usage**
+
+```python
+speech_file_path = Path(__file__).parent / "speech_vertex.mp3"
+response = litellm.speech(
+    input=None,
+    model="vertex_ai/test",
+    ssml="async hello what llm guardrail do you have",
+    voice={
+        "languageCode": "en-UK",
+        "name": "en-UK-Studio-O",
+    },
+    audioConfig={
+        "audioEncoding": "LINEAR22",
+        "speakingRate": "10",
+    },
+)
+response.stream_to_file(speech_file_path)
+```
+
+</TabItem>
+
+<TabItem value="proxy" label="LiteLLM PROXY (Unified Endpoint)">
+
+```python
+import openai
+
+client = openai.OpenAI(api_key="sk-1234", base_url="http://0.0.0.0:4000")
+
+# see supported values for "voice" on vertex here: 
+# https://console.cloud.google.com/vertex-ai/generative/speech/text-to-speech
+response = client.audio.speech.create(
+    model = "vertex-tts",
+    input=None, # pass as None since OpenAI SDK requires this param
+    voice={'languageCode': 'en-US', 'name': 'en-US-Studio-O'},
+    extra_body={
+        "ssml": "async hello what llm guardrail do you have"
+    }
+)
+print("response from proxy", response)
+```
+
+</TabItem>
+</Tabs>
+
+
+
 ## Extra
 
 ### Using `GOOGLE_APPLICATION_CREDENTIALS`