Improve error message for when nnx.Modules use jax or numpy arrays as…

… leaf values

flax/nnx/graph.py

@@ -446,7 +446,8 @@ def _graph_flatten(
       if isinstance(value, (jax.Array, np.ndarray)):
         path_str = '/'.join(map(str, (*path, key)))
         raise ValueError(
-            f'Arrays leaves are not supported, at {path_str!r}: {value}'
+            f'The variable at the path {path_str!r} with value = {value} is of type:' \
+            f'{type(value)}. Leaf values of this type are not supported for nnx.Modules.'
         )
       # static_fields.append((key, value))
       attributes.append(StaticAttribute(key, value))