Changed the default embedding model to openai. (#1087)

* Removed duplicate code in query execution.

* Added nltk download logic to support string metrics.

* Add ragas to imports.

* Added ragas to imports.

* Added string metrics for evaluation.

* Remove dthe unwanted break statement.

* Moves the import to top of file.

* Moved the scorer definitions to the init function.

* Refactoring.

* Removed unused imports.

* Moved async calls to the outer function.

* Refactor to add error handling and change function names.

* Added correctness score to metrics.

* Changed the default embedding model to openai.

* Removed unused imports.

* Removed unused Huggingface embeddings method.

apps/query-eval/queryeval/driver.py

@@ -26,7 +26,10 @@
 import asyncio
 from ragas.dataset_schema import SingleTurnSample
 from ragas.metrics import BleuScore, RougeScore, SemanticSimilarity
-from ragas.embeddings.base import HuggingfaceEmbeddings, LangchainEmbeddingsWrapper
+from ragas.embeddings.base import (
+    OpenAIEmbeddings,
+    LangchainEmbeddingsWrapper,
+)
 from ragas.metrics._factual_correctness import FactualCorrectness
 from langchain_openai.chat_models import ChatOpenAI
 from ragas.llms import LangchainLLMWrapper
@@ -195,7 +198,7 @@ def __init__(
         self.rouge_scorer = RougeScore()
         self.semantic_similarity_scorer = SemanticSimilarity()
         self.semantic_similarity_scorer.embeddings = LangchainEmbeddingsWrapper(
-            HuggingfaceEmbeddings(model_name="sentence-transformers/all-MiniLM-L6-v2")
+            OpenAIEmbeddings(model="text-embedding-3-small")
         )
         self.correctness_scorer = FactualCorrectness()
         self.correctness_scorer.llm = LangchainLLMWrapper(ChatOpenAI(model="gpt-4o"))