fix: Python 3.9 compatibility - replace union types and builtin generics

- Replace 'str | None' with 'Optional[str]'
- Replace 'list[str]' with 'List[str]'
- Replace 'dict[' with 'Dict['
- Replace 'tuple[' with 'Tuple['
- Add missing typing imports (List, Dict, Tuple)

Fixes TypeError: unsupported operand type(s) for |: 'type' and 'NoneType'

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

packages/leann-backend-diskann/leann_backend_diskann/diskann_backend.py

@@ -4,7 +4,7 @@ import os
 import struct
 import sys
 from pathlib import Path
-from typing import Any, Literal, Optional
+from typing import Any, Dict, List, Literal, Optional, Tuple
 
 import numpy as np
 import psutil
@@ -85,7 +85,7 @@ def _write_vectors_to_bin(data: np.ndarray, file_path: Path):
         f.write(data.tobytes())
 
 
-def _calculate_smart_memory_config(data: np.ndarray) -> tuple[float, float]:
+def _calculate_smart_memory_config(data: np.ndarray) -> Tuple[float, float]:
     """
     Calculate smart memory configuration for DiskANN based on data size and system specs.
 
@@ -202,7 +202,7 @@ class DiskannBuilder(LeannBackendBuilderInterface):
                     size_mb = file_path.stat().st_size / (1024 * 1024)
                     logger.info(f"  - {filename} ({size_mb:.1f} MB)")
 
-    def build(self, data: np.ndarray, ids: list[str], index_path: str, **kwargs):
+    def build(self, data: np.ndarray, ids: List[str], index_path: str, **kwargs):
         path = Path(index_path)
         index_dir = path.parent
         index_prefix = path.stem
@@ -388,7 +388,7 @@ class DiskannSearcher(BaseSearcher):
         batch_recompute: bool = False,
         dedup_node_dis: bool = False,
         **kwargs,
-    ) -> dict[str, Any]:
+    ) -> Dict[str, Any]:
         """
         Search for nearest neighbors using DiskANN index.
 

packages/leann-backend-diskann/leann_backend_diskann/graph_partition.py

@@ -12,7 +12,7 @@ import shutil
 import subprocess
 import tempfile
 from pathlib import Path
-from typing import Optional
+from typing import Optional, Tuple
 
 
 class GraphPartitioner:
@@ -92,7 +92,7 @@ class GraphPartitioner:
         output_dir: Optional[str] = None,
         partition_prefix: Optional[str] = None,
         **kwargs,
-    ) -> tuple[str, str]:
+    ) -> Tuple[str, str]:
         """
         Partition a disk-based index for improved performance.
 
@@ -263,11 +263,11 @@ class GraphPartitioner:
 
 def partition_graph(
     index_prefix_path: str,
-    output_dir: str | None = None,
-    partition_prefix: str | None = None,
+    output_dir: Optional[str] = None,
+    partition_prefix: Optional[str] = None,
     build_type: str = "release",
     **kwargs,
-) -> tuple[str, str]:
+) -> Tuple[str, str]:
     """
     Convenience function to partition a graph index.
 

packages/leann-backend-diskann/leann_backend_diskann/graph_partition_simple.py

@@ -15,7 +15,7 @@ from typing import Optional
 
 def partition_graph_simple(
     index_prefix_path: str, output_dir: Optional[str] = None, **kwargs
-) -> tuple[str, str]:
+) -> Tuple[str, str]:
     """
     Simple function to partition a graph index.