[verl] Modify the update_weights func to align with verl's resharding (#5345)

Co-authored-by: Chayenne <zhaochen20@outlook.com>

python/sglang/srt/entrypoints/verl_engine.py

@@ -12,7 +12,7 @@
 # limitations under the License.
 # ==============================================================================
 import os
-from typing import Dict, List, Literal, Optional, Tuple, Union
+from typing import Dict, Iterable, List, Literal, Optional, Tuple, Union
 
 import torch
 import torch.distributed as dist
@@ -124,7 +124,7 @@ class VerlEngine:
 
     def update_weights_from_tensor(
         self,
-        named_tensors: List[Tuple[str, torch.Tensor]],
+        named_tensors: Iterable[Tuple[str, torch.Tensor]],
         load_format: Optional[str] = None,
     ):
         # Most naive implementation, can optimize a lot if it is bottleneck
@@ -153,9 +153,12 @@ class VerlEngine:
                         )
                     ],
                     load_format=load_format,
-                    flush_cache=tensor_index == len(named_tensors) - 1,
+                    flush_cache=False,
                 )
 
+        if self._tp_rank == 0:
+            self._engine.tokenizer_manager.flush_cache()
+
     def release_memory_occupation(self):
         if self._tp_rank == 0:
             self._engine.release_memory_occupation()