fix: Remove a prop

Author: tmathern

src/c2pa/c2pa.py

@@ -1997,15 +1997,6 @@ def reserve_size(self) -> int:
 
         return result
 
-    @property
-    def closed(self) -> bool:
-        """Check if the signer is closed.
-
-        Returns:
-            bool: True if the signer is closed, False otherwise
-        """
-        return self._closed
-
 
 class Builder:
     """High-level wrapper for C2PA Builder operations."""

tests/test_unit_tests.py

@@ -443,7 +443,7 @@ def test_reserve_size_on_closed_signer(self):
         )
         signer = Signer.from_info(signer_info)
         signer.close()
-        self.assertTrue(signer.closed)
+        # Verify signer is closed by testing that operations fail
         with self.assertRaises(Error):
             signer.reserve_size()
 
@@ -456,7 +456,7 @@ def test_signer_double_close(self):
         )
         signer = Signer.from_info(signer_info)
         signer.close()
-        self.assertTrue(signer.closed)
+        # Second close should not raise an exception
         signer.close()
 
     def test_builder_detects_malformed_json(self):