cache replicate version (langchain-ai#10517)

In subsequent pr will update _call to use replicate.run directly when
not streaming, so version object isn't needed at all

cc @cbh123 @tjaffri

libs/langchain/langchain/llms/replicate.py

@@ -1,3 +1,5 @@
+from __future__ import annotations
+
 import logging
 from typing import Any, Dict, List, Optional
 
@@ -23,17 +25,26 @@ class Replicate(LLM):
         .. code-block:: python
 
             from langchain.llms import Replicate
-            replicate = Replicate(model="stability-ai/stable-diffusion: \
-                                         27b93a2413e7f36cd83da926f365628\
-                                         0b2931564ff050bf9575f1fdf9bcd7478",
-                                  input={"image_dimensions": "512x512"})
+
+            replicate = Replicate(
+                model=(
+                    "stability-ai/stable-diffusion: "
+                    "27b93a2413e7f36cd83da926f3656280b2931564ff050bf9575f1fdf9bcd7478",
+                ),
+                input={"image_dimensions": "512x512"}
+            )
     """
 
     model: str
     input: Dict[str, Any] = Field(default_factory=dict)
     model_kwargs: Dict[str, Any] = Field(default_factory=dict)
     replicate_api_token: Optional[str] = None
     prompt_key: Optional[str] = None
+    version_obj: Any = Field(default=None, exclude=True)
+    """Optionally pass in the model version object during initialization to avoid 
+        having to make an extra API call to retrieve it during streaming. NOTE: not
+        serializable, is excluded from serialization.
+    """
 
     streaming: bool = Field(default=False)
     """Whether to stream the results."""
@@ -111,14 +122,15 @@ def _call(
             )
 
         # get the model and version
-        model_str, version_str = self.model.split(":")
-        model = replicate_python.models.get(model_str)
-        version = model.versions.get(version_str)
+        if self.version_obj is None:
+            model_str, version_str = self.model.split(":")
+            model = replicate_python.models.get(model_str)
+            self.version_obj = model.versions.get(version_str)
 
-        if not self.prompt_key:
+        if self.prompt_key is None:
             # sort through the openapi schema to get the name of the first input
             input_properties = sorted(
-                version.openapi_schema["components"]["schemas"]["Input"][
+                self.version_obj.openapi_schema["components"]["schemas"]["Input"][
                     "properties"
                 ].items(),
                 key=lambda item: item[1].get("x-order", 0),
@@ -129,7 +141,7 @@ def _call(
         inputs: Dict = {self.prompt_key: prompt, **self.input}
 
         prediction = replicate_python.predictions.create(
-            version=version, input={**inputs, **kwargs}
+            version=self.version_obj, input={**inputs, **kwargs}
         )
         current_completion: str = ""
         stop_condition_reached = False