Add option to import OpenAIEmbeddings from langchain_openai (#328)

`OpenAIEmbeddings` was removed from the main langchain repo and needs to be imported from `langchain_openai` for newer langchain versions.

Author: NikolaosPapailiou

apis/python/src/tiledb/vector_search/embeddings/langchain_embedding.py

@@ -8,7 +8,11 @@
 # class LangChainEmbedding(ObjectEmbedding):
 class LangChainEmbedding:
     """
-    Embedding functions from `langchain.embeddings` package.
+    Embedding functions from Langchain.
+
+    This attempts to import the embedding_class from the following modules:
+    - langchain_openai
+    - langchain.embeddings
     """
 
     def __init__(
@@ -37,9 +41,14 @@ def vector_type(self) -> np.dtype:
     def load(self) -> None:
         import importlib
 
-        embeddings_module = importlib.import_module("langchain.embeddings")
-        embedding_class_ = getattr(embeddings_module, self.embedding_class)
-        self.embedding = embedding_class_(**self.embedding_kwargs)
+        try:
+            embeddings_module = importlib.import_module("langchain_openai")
+            embedding_class_ = getattr(embeddings_module, self.embedding_class)
+            self.embedding = embedding_class_(**self.embedding_kwargs)
+        except ImportError:
+            embeddings_module = importlib.import_module("langchain.embeddings")
+            embedding_class_ = getattr(embeddings_module, self.embedding_class)
+            self.embedding = embedding_class_(**self.embedding_kwargs)
 
     def embed(self, objects: OrderedDict, metadata: OrderedDict) -> np.ndarray:
         return np.array(