fixed import error and disabled gpu usage

app.py

@@ -1,6 +1,14 @@
 import os
 
 import streamlit as st
+from haystack.document_stores import FAISSDocumentStore
+from haystack.utils import convert_files_to_docs, fetch_archive_from_http, clean_wiki_text
+from haystack.nodes import DensePassageRetriever
+from haystack.utils import print_documents, print_answers
+from haystack.pipelines import DocumentSearchPipeline
+from haystack.nodes import Seq2SeqGenerator
+from haystack.pipelines import GenerativeQAPipeline
+from haystack.utils import convert_files_to_docs, clean_wiki_text
 
 from lfqa import prepare, answer
 
@@ -124,10 +132,6 @@ def main(pipe):
 
 # %% ------------------------------------------- Creating Doc store
 # if not os.path.exists(sql_file) or not os.path.exists(faiss_file):
-from haystack.document_stores import FAISSDocumentStore
-from haystack.nodes import DensePassageRetriever
-from haystack.utils import convert_files_to_docs, clean_wiki_text
-
 
 module_dir = os.path.dirname(os.path.abspath(__file__))
 os.chdir(module_dir) 
@@ -163,7 +167,7 @@ retriever = DensePassageRetriever(
     document_store=document_store,
     query_embedding_model="vblagoje/dpr-question_encoder-single-lfqa-wiki",
     passage_embedding_model="vblagoje/dpr-ctx_encoder-single-lfqa-wiki",
-    use_gpu=True
+    use_gpu=False
 )
 
 # %% Create Embeddings  and save results