docs: Add reranking example (#243)

* docs: Add reranking example

* chore: Added top_n to the example

Author: tazarov

README.md

@@ -209,6 +209,29 @@ embeddings = get_embeddings(input_texts, model='togethercomputer/m2-bert-80M-8k-
 print(embeddings)
 ```
 
+### Reranking
+
+```python
+from typing import List
+from together import Together
+
+client = Together(api_key=os.environ.get("TOGETHER_API_KEY"))
+
+def get_reranked_documents(query: str, documents: List[str], model: str, top_n: int = 3) -> List[str]:
+    outputs = client.rerank.create(model=model, query=query, documents=documents, top_n=top_n)
+    # sort by relevance score and returns the original docs
+    return [documents[i] for i in [x.index for x in sorted(outputs.results, key=lambda x: x.relevance_score, reverse=True)]]
+
+query = "What is the capital of the United States?"
+documents = ["New York","Washington, D.C.", "Los Angeles"]
+
+reranked_documents = get_reranked_documents(query, documents, model='Salesforce/Llama-Rank-V1', top_n=1)
+
+print(reranked_documents)
+```
+
+Read more about Reranking [here](https://docs.together.ai/docs/rerank-overview).
+
 ### Files
 
 The files API is used for fine-tuning and allows developers to upload data to fine-tune on. It also has several methods to list all files, retrive files, and delete files. Please refer to our fine-tuning docs [here](https://docs.together.ai/docs/fine-tuning-python).