improve MongoDB client management and storage init

examples/lightrag_api_oracle_demo.py

@@ -17,7 +17,6 @@ from lightrag.llm.openai import openai_complete_if_cache, openai_embed
 from lightrag.utils import EmbeddingFunc
 import numpy as np
 
-from lightrag.kg.oracle_impl import OracleDB
 
 print(os.getcwd())
 script_directory = Path(__file__).resolve().parent.parent

examples/lightrag_oracle_demo.py

@@ -6,7 +6,6 @@ from lightrag import LightRAG, QueryParam
 from lightrag.llm.openai import openai_complete_if_cache, openai_embed
 from lightrag.utils import EmbeddingFunc
 import numpy as np
-from lightrag.kg.oracle_impl import OracleDB
 
 print(os.getcwd())
 script_directory = Path(__file__).resolve().parent.parent

examples/lightrag_tidb_demo.py

@@ -4,7 +4,6 @@ import os
 import numpy as np
 
 from lightrag import LightRAG, QueryParam
-from lightrag.kg.tidb_impl import TiDB
 from lightrag.llm import siliconcloud_embedding, openai_complete_if_cache
 from lightrag.utils import EmbeddingFunc
 

examples/lightrag_zhipu_postgres_demo.py

@@ -5,7 +5,6 @@ import time
 from dotenv import load_dotenv
 
 from lightrag import LightRAG, QueryParam
-from lightrag.kg.postgres_impl import PostgreSQLDB
 from lightrag.llm.zhipu import zhipu_complete
 from lightrag.llm.ollama import ollama_embedding
 from lightrag.utils import EmbeddingFunc