Readded similarity_search_by_vector (#1568)

I am redoing this PR, as I made a mistake by merging the latest changes
into my fork's branch, sorry. This added a bunch of commits to my
previous PR.

This fixes #1451.

langchain/vectorstores/chroma.py

@@ -16,6 +16,23 @@ if TYPE_CHECKING:
 logger = logging.getLogger()
 
 
+def _results_to_docs(results: Any) -> List[Document]:
+    return [doc for doc, _ in _results_to_docs_and_scores(results)]
+
+
+def _results_to_docs_and_scores(results: Any) -> List[Tuple[Document, float]]:
+    return [
+        # TODO: Chroma can do batch querying,
+        # we shouldn't hard code to the 1st result
+        (Document(page_content=result[0], metadata=result[1]), result[2])
+        for result in zip(
+            results["documents"][0],
+            results["metadatas"][0],
+            results["distances"][0],
+        )
+    ]
+
+
 class Chroma(VectorStore):
     """Wrapper around ChromaDB embeddings platform.
 
@@ -126,6 +143,22 @@ class Chroma(VectorStore):
         docs_and_scores = self.similarity_search_with_score(query, k)
         return [doc for doc, _ in docs_and_scores]
 
+    def similarity_search_by_vector(
+        self,
+        embedding: List[float],
+        k: int = 4,
+        **kwargs: Any,
+    ) -> List[Document]:
+        """Return docs most similar to embedding vector.
+        Args:
+            embedding: Embedding to look up documents similar to.
+            k: Number of Documents to return. Defaults to 4.
+        Returns:
+            List of Documents most similar to the query vector.
+        """
+        results = self._collection.query(query_embeddings=embedding, n_results=k)
+        return _results_to_docs(results)
+
     def similarity_search_with_score(
         self,
         query: str,
@@ -154,17 +187,7 @@ class Chroma(VectorStore):
                 query_embeddings=[query_embedding], n_results=k, where=filter
             )
 
-        docs = [
-            # TODO: Chroma can do batch querying,
-            # we shouldn't hard code to the 1st result
-            (Document(page_content=result[0], metadata=result[1]), result[2])
-            for result in zip(
-                results["documents"][0],
-                results["metadatas"][0],
-                results["distances"][0],
-            )
-        ]
-        return docs
+        return _results_to_docs_and_scores(results)
 
     def delete_collection(self) -> None:
         """Delete the collection."""