Fix/add type hints and decorators

[pranavkonde]

Description

Improved type safety and code clarity by adding proper type hints and method decorators to the SDK class.

Changes

1. Added @staticmethod decorator to extract_block_data
2. Added return type hints to all methods:
   • __init__ -> None
   • close -> None
   • streaming_api -> StreamingAPI
   • ipc -> IPC
   • create_bucket -> BucketCreateResult
   • view_bucket -> Bucket
   • delete_bucket -> None
   • extract_block_data -> bytes
   • encryption_key_derivation -> Optional[bytes]
3. Added proper type hints for class attributes:
   • client: Optional[nodeapi_pb2_grpc.NodeAPIStub]
   • conn: Optional[grpc.Channel]
   • sp_client: Optional[SPClient]
   • streaming_erasure_code: Optional[ErasureCode]
4. Fixed code style:
   • Fixed indentation in extract_block_data method
   • Added proper spacing between classes
   • Improved code readability