fix last_seen_indices dtype

PiperOrigin-RevId: 877639205

Author: Grain Team

grain/_src/python/data_loader.py

@@ -273,7 +273,7 @@ def get_state(self):
 
     local_offset = shard_index - global_worker_count
     last_seen_indices = {
-        str(i): (
+        str(i): int(
             local_offset
             + i * shard_count
             + workers_state[i]["next_index"] * global_worker_count