Stop writing msgpack file for new checkpoints and update empty nodes …

…handling so that it no longer depends on this file.

PiperOrigin-RevId: 636665054

init2winit/test_utils.py

@@ -97,15 +97,18 @@ def testAppendPytree(self):
     latest = checkpoint.load_latest_checkpoint(pytree_path, prefix='')
     saved_pytrees = latest['pytree'] if latest else []
     self.assertEqual(
-        pytrees, [saved_pytrees[str(i)] for i in range(len(saved_pytrees))])
+        pytrees, [saved_pytrees[str(i)] for i in range(len(saved_pytrees))]
+    )
 
   def testArrayAppend(self):
     """Test appending to an array."""
     np.testing.assert_allclose(
-        utils.array_append(jnp.array([1, 2, 3]), 4), jnp.array([1, 2, 3, 4]))
+        utils.array_append(jnp.array([1, 2, 3]), 4), jnp.array([1, 2, 3, 4])
+    )
     np.testing.assert_allclose(
         utils.array_append(jnp.array([[1, 2], [3, 4]]), jnp.array([5, 6])),
-        jnp.array([[1, 2], [3, 4], [5, 6]]))
+        jnp.array([[1, 2], [3, 4], [5, 6]]),
+    )
 
   def testTreeNormSqL2(self):
     """Test computing the squared L2 norm of a pytree."""
@@ -115,9 +118,9 @@ def testTreeNormSqL2(self):
 
   def testTreeSum(self):
     """Test computing the sum of a pytree."""
-    pytree = {'foo': 2*jnp.ones(10), 'baz': jnp.ones(20)}
+    pytree = {'foo': 2 * jnp.ones(10), 'baz': jnp.ones(20)}
     self.assertEqual(utils.total_tree_sum(pytree), 40)
 
+
 if __name__ == '__main__':
   absltest.main()
-