core[minor]: Add default implementations to amax_marginal_relevance_search_by_vector and adelete (#19269)

libs/core/langchain_core/vectorstores.py

@@ -112,8 +112,7 @@ class VectorStore(ABC):
             Optional[bool]: True if deletion is successful,
             False otherwise, None if not implemented.
         """
-
-        raise NotImplementedError("delete method must be implemented by subclass.")
+        return await run_in_executor(None, self.delete, ids, **kwargs)
 
     async def aadd_texts(
         self,
@@ -513,7 +512,15 @@ class VectorStore(ABC):
         **kwargs: Any,
     ) -> List[Document]:
         """Return docs selected using the maximal marginal relevance."""
-        raise NotImplementedError
+        return await run_in_executor(
+            None,
+            self.max_marginal_relevance_search_by_vector,
+            embedding,
+            k=k,
+            fetch_k=fetch_k,
+            lambda_mult=lambda_mult,
+            **kwargs,
+        )
 
     @classmethod
     def from_documents(