fix: address final PR review feedback (lint, types, docs)

- tests: rename test_save_and_load_rsa_identity to test_overwrite_existing_identity to match behavior
- tests: add missing return type annotations for mypy compliance
- build: fix linting issues (trailing whitespace, imports)
- docs: add identity persistence note to README.md

Author: Smartdevs17

README.md

@@ -115,6 +115,12 @@ ______________________________________________________________________
 
 ______________________________________________________________________
 
+### Identity Persistence
+
+For a stable Peer ID across restarts, see `libp2p.identity_utils`. You can save/load identities to disk or create deterministic identities from a seed.
+
+______________________________________________________________________
+
 ## Explanation of Basic Two Node Communication
 
 ### Core Concepts

tests/core/test_identity_persistence_enhanced.py

@@ -9,28 +9,28 @@
 """
 
 import os
+from pathlib import Path
 import stat
 import tempfile
-from pathlib import Path
 
 import pytest
 
 from libp2p.crypto.ed25519 import create_new_key_pair
 from libp2p.identity_utils import load_identity, save_identity
 
 
-def test_save_identity_sets_restrictive_permissions():
+def test_save_identity_sets_restrictive_permissions() -> None:
     """
     Verify that saved identity files have restrictive permissions (0600).
-    
+
     This is a security requirement to prevent other users from reading
     the private key file.
     """
     with tempfile.TemporaryDirectory() as tmpdir:
         filepath = Path(tmpdir) / "test_identity.key"
         key_pair = create_new_key_pair()
         save_identity(key_pair, filepath)
-        
+
         # Check file permissions (Unix-like systems only)
         if os.name != "nt":  # Skip on Windows
             mode = filepath.stat().st_mode
@@ -41,102 +41,97 @@ def test_save_identity_sets_restrictive_permissions():
             )
 
 
-def test_load_corrupted_identity_raises_error():
+def test_load_corrupted_identity_raises_error() -> None:
     """
     Verify that loading a corrupted identity file raises ValueError.
-    
+
     This ensures we don't silently accept invalid key data.
     """
     with tempfile.TemporaryDirectory() as tmpdir:
         filepath = Path(tmpdir) / "corrupted.key"
         # Write invalid data
         filepath.write_bytes(b"not a valid private key")
-        
+
         with pytest.raises(ValueError, match="Invalid or corrupted"):
             load_identity(filepath)
 
 
-def test_load_truncated_file_raises_error():
+def test_load_truncated_file_raises_error() -> None:
     """
     Verify that loading a truncated file raises ValueError.
-    
+
     Truncated files could result from interrupted writes.
     """
     with tempfile.TemporaryDirectory() as tmpdir:
         filepath = Path(tmpdir) / "truncated.key"
         # Write only a few bytes (truncated protobuf)
         filepath.write_bytes(b"\x00\x01\x02")
-        
+
         with pytest.raises(ValueError, match="Invalid or corrupted"):
             load_identity(filepath)
 
 
-def test_load_empty_file_raises_error():
+def test_load_empty_file_raises_error() -> None:
     """
     Verify that loading an empty file raises ValueError.
     """
     with tempfile.TemporaryDirectory() as tmpdir:
         filepath = Path(tmpdir) / "empty.key"
         # Write empty file
         filepath.write_bytes(b"")
-        
+
         with pytest.raises(ValueError, match="Invalid or corrupted"):
             load_identity(filepath)
 
 
-def test_save_and_load_rsa_identity():
+def test_overwrite_existing_identity() -> None:
     """
     Test that saving to an existing file overwrites it correctly.
-    
+
     This ensures we can update identity files without errors.
     """
     with tempfile.TemporaryDirectory() as tmpdir:
         filepath = Path(tmpdir) / "identity.key"
-        
+
         # Save first identity
         key_pair_1 = create_new_key_pair()
         save_identity(key_pair_1, filepath)
-        
+
         # Overwrite with second identity
         key_pair_2 = create_new_key_pair()
         save_identity(key_pair_2, filepath)
-        
+
         # Load and verify it's the second identity
         loaded_key_pair = load_identity(filepath)
         assert (
-            loaded_key_pair.private_key.to_bytes()
-            == key_pair_2.private_key.to_bytes()
+            loaded_key_pair.private_key.to_bytes() == key_pair_2.private_key.to_bytes()
         )
         assert (
-            loaded_key_pair.private_key.to_bytes()
-            != key_pair_1.private_key.to_bytes()
+            loaded_key_pair.private_key.to_bytes() != key_pair_1.private_key.to_bytes()
         )
 
 
-def test_save_identity_creates_parent_directories():
+def test_save_identity_creates_parent_directories() -> None:
     """
     Test that save_identity creates parent directories if they don't exist.
-    
+
     This prevents FileNotFoundError when saving to nested paths.
     """
     with tempfile.TemporaryDirectory() as tmpdir:
-        # Use a nested path that doesn't exist
+        # Use a nested path that doesn't exis
         filepath = Path(tmpdir) / "nested" / "dir" / "identity.key"
-        
-        # Parent directories don't exist yet
+
+        # Parent directories don't exist ye
         assert not filepath.parent.exists()
-        
+
         # Save should create them
         key_pair = create_new_key_pair()
         save_identity(key_pair, filepath)
-        
+
         # Verify file was created
         assert filepath.exists()
         assert filepath.parent.exists()
-        
-        # Verify we can load it
+
+        # Verify we can load i
         loaded_key_pair = load_identity(filepath)
-        assert (
-            loaded_key_pair.private_key.to_bytes()
-            == key_pair.private_key.to_bytes()
-        )
+        assert loaded_key_pair.private_key.to_bytes() == key_pair.private_key.to_bytes()