ChromaDB ParentDocumentRetriever.get_relevant_documents not returning docs despite similarity_search returning matching docs
Labels: name: area: doc loader, name: auto:bug, name: integration: chroma

### System Info

LangChain 0.0.354, Python 3.11

### Who can help?

@hwchase17
@agola11

### Information

- [ ] The official example notebooks/scripts
- [X] My own modified scripts

### Related Components

- [X] LLMs/Chat Models
- [ ] Embedding Models
- [ ] Prompts / Prompt Templates / Prompt Selectors
- [ ] Output Parsers
- [X] Document Loaders
- [X] Vector Stores / Retrievers
- [ ] Memory
- [ ] Agents / Agent Executors
- [ ] Tools / Toolkits
- [ ] Chains
- [ ] Callbacks/Tracing
- [ ] Async

### Reproduction

Embedded 1000 or so documents and did a vector similarity search. Came back with a lot of good results. Did the get_relevant_documents call but had no returns. LLM also did not.

My retriever is:

- ParentDocumentRetriever with a parent_splitter and child_splitter
- Parent splits at 2000 tokens. Child splits at 400.

```python
def load_chroma_db(collection_name: str):
    parent_splitter = RecursiveCharacterTextSplitter(chunk_size=2000)
    child_splitter = RecursiveCharacterTextSplitter(chunk_size=400)

    vectorstore = None
    try:
        vectorstore = Chroma(persist_directory="storage/deploy/chroma-db", embedding_function=get_embedding_function())        
        print("Loaded existing vector store")
    except:
        print("Creating new vector store")
        vectorstore = Chroma(
            collection_name=collection_name, 
            embedding_function=get_embedding_function(), 
            persist_directory="storage/deploy/chroma-db"
        )
        
    store = InMemoryStore()
    
    retriever = ParentDocumentRetriever(
        vectorstore=vectorstore,
        docstore=store,
        child_splitter=child_splitter,
        parent_splitter=parent_splitter
    )
    return retriever

retriever = load_chroma_db("full_docs")
retriever.vectorstore.similarity_search_with_score("How do I make a zelle transaction?")
```

This returns 
```python
[(Document(page_content='Basic Introduction to Zelle® What is Zelle®? Zelle® is a fast, safe, and easy way for members to send money directly between most bank or credit union accounts in the U.S. These Person- to- Person transactions typically occur within minutes. With just an email address or U.S. mobile phone number, members can send money to friends, family, and people they know and trust, regardless of where they', metadata={'date_day': 27, 'date_month': 4, 'date_year': 2023, 'doc_id': '22bfa535-8bc7-4a97-8270-d84b77ba81b0', 'source': 'storage/Bancworks/Zelle & CST FAQs - Internal Use.pdf.txt'}),
  0.24197007715702057),
 (Document(page_content='Basic Introduction to Zelle® ......................................... 2 Zelle® Transaction Limits / Tiers ............................. 2 Enrollment / Eligible Accounts ................................ 3 Sending / Receiving Transactions ........................... 4 Disputes / Fraud / Scams ......................................... 5 Customer Service Tool (CST)', metadata={'date_day': 27, 'date_month': 4, 'date_year': 2023, 'doc_id': 'eb27b502-c37c-4462-9d8b-488b53c3aa11', 'source': 'storage/Bancworks/Zelle & CST FAQs - Internal Use.pdf.txt'}),
  0.24453413486480713),
 (Document(page_content='Step 1: Find Zelle in the main menu of the Kinecta mobile banking app. Step 2: Enroll with a U.S. mobile number or email address and select a checking account. Step 3: Start using Zelle. Talking Points: • Zelle is a fast, safe and easy way to send money directly between almost any checking or savings accounts in the U.S., typically within minutes. • With just an email address or U.S. mobile phone', metadata={'date_day': 28, 'date_month': 4, 'date_year': 2023, 'doc_id': '161170fc-8871-412d-a0e7-47e4b1b3d889', 'source': 'storage/Bancworks/Zelle - MarketGram - 20230502.pdf.txt'}),
  0.2447606921195984),
 (Document(page_content='• Zelle is a fast, safe and easy way to send money directly between almost any checking or savings accounts in the U.S., typically within minutes. • With just an email address or U.S. mobile phone number, send money to people you trust, regardless of where they bank. • Transactions between enrolled consumers typically occur in minutes and generally do not incur transaction fees. • Send, split or', metadata={'date_day': 28, 'date_month': 4, 'date_year': 2023, 'doc_id': '161170fc-8871-412d-a0e7-47e4b1b3d889', 'source': 'storage/Bancworks/Zelle - MarketGram - 20230502.pdf.txt'}),
  0.2502959370613098)]
```

If I do the following call:
```python
retriever.get_relevant_documents("How do I make a zelle transaction?", k=4)
```

I get nothing returned.
```python
[]
```

### Expected behavior

Parent documents should be returned based on the child embeddings found.