Nested dictionaries error about dbus-rs HOT 8 CLOSED

process 25101: arguments to dbus_message_iter_open_container() were incorrect, assertion "(type == DBUS_TYPE_ARRAY && contained_signature && *contained_signature == DBUS_DICT_ENTRY_BEGIN_CHAR) || (contained_signature == NULL || _dbus_check_is_valid_signature (contained_signature))" failed in file ../../dbus/dbus-message.c line 2801.
This is normally a bug in some application using the D-Bus library.

let m: MessageItem =  /* ... */;
println!("{:?}", m); // I want this output
message.append_items(&[m]);

Array([
  DictEntry( Str("org.freedesktop.Secret.Item.Label"), Variant(Str("Test")) ),
  DictEntry( Str("org.freedesktop.Secret.Item.Attributes"), Variant( Array([DictEntry(Str("one"), Str("one"))], "{ss}")))
], "{sv}")

Array([DictEntry(Str("org.freedesktop.Secret.Item.Label"), Variant(Str("Test"))), DictEntry(Str("org.freedesktop.Secret.Item.Attributes"), Variant(Array([DictEntry(Str("one"), Str("one"))], "{ss}")))], "{sv}")

---- item::test::should_get_and_set_item_attributes stdout ----
Array([DictEntry(Str("test"), Str("test"))], "{ss}")
thread 'item::test::should_get_and_set_item_attributes' panicked at 'assertion failed: unsafe {
    ffi::dbus_message_iter_open_container(i, ffi::DBUS_TYPE_VARIANT,
                                          atype.as_ptr(), &mut subiter)
} != 0', /home/hwchen/.cargo/registry/src/github.com-88ac128001ac3a9a/dbus-0.2.2/src/message.rs:156