fix(kg): resolve 'unhashable type: Entity' in GraphAnalyzer #159

- Robust ID extraction in CentralityCalculator, CommunityDetector, and ConnectivityAnalyzer
- Support for direct Entity objects and dictionaries as node identifiers
- Improved Entity hashability in utils/types.py
- Added integration test to verify fix and prevent regression

tests/normalize/test_encoding_handler.py

@@ -0,0 +1,43 @@
+import unittest
+import os
+from semantica.normalize.encoding_handler import EncodingHandler
+
+class TestEncodingHandler(unittest.TestCase):
+    def setUp(self):
+        self.handler = EncodingHandler()
+
+    def test_detect_encoding(self):
+        # UTF-8
+        text = "Héllò Wörld"
+        utf8_bytes = text.encode("utf-8")
+        encoding, conf = self.handler.detect(utf8_bytes)
+        self.assertEqual(encoding.lower(), "utf-8")
+        
+        # Latin-1
+        latin1_bytes = text.encode("latin-1")
+        encoding, conf = self.handler.detect(latin1_bytes)
+        # chardet might return ISO-8859-1 or Windows-1252 which are compatible
+        self.assertIn(encoding.lower(), ["iso-8859-1", "windows-1252", "latin-1"])
+
+    def test_convert_to_utf8(self):
+        text = "Héllò Wörld"
+        latin1_bytes = text.encode("latin-1")
+        converted = self.handler.convert_to_utf8(latin1_bytes)
+        self.assertEqual(converted, text)
+
+    def test_remove_bom(self):
+        # UTF-8 BOM
+        bom_bytes = b"\xef\xbb\xbfHello"
+        self.assertEqual(self.handler.remove_bom(bom_bytes), b"Hello")
+        
+        # String BOM
+        bom_str = "\ufeffHello"
+        self.assertEqual(self.handler.remove_bom(bom_str), "Hello")
+
+    def test_validate_encoding(self):
+        self.assertTrue(self.handler.validate_encoding("Hello", "utf-8"))
+        # Invalid sequence for ascii
+        self.assertFalse(self.handler.validate_encoding("Héllò", "ascii"))
+
+if __name__ == "__main__":
+    unittest.main()