feat: first version of prompt caching

anthropic_prompt_caching.py

@@ -0,0 +1,33 @@
+from pydantic import BaseModel, Field
+from typing import Optional
+
+class Filter:
+    class Valves(BaseModel):
+        pass
+
+    def __init__(self):
+        self.valves = self.Valves()
+        self.toggle = True # IMPORTANT: This creates a switch UI in Open WebUI
+        pass
+
+    async def inlet(
+        self, body: dict, __event_emitter__, __user__: Optional[dict] = None
+    ) -> dict:
+        await __event_emitter__(
+            {
+                "type": "status",
+                "data": {
+                    "description": "Prompt Caching Enabled!",
+                    "done": True,
+                    "hidden": False,
+                },
+            }
+        )
+        print("Prompt Caching Enabled!")
+        last_message_item = body["messages"][-1]
+        # 如果 content 是字符串
+        if isinstance(last_message_item["content"], str):
+            last_message_item['content'] = [{"type": "text", "text": last_message_item["content"], "cache_control": {"type": "ephemeral"}}]
+        else:
+            print("Prompt Caching Failed: unsupported content type")
+        return body