Fix BatchMambaCache missing size arg for mlx-lm >= 0.30.6

vllm_mlx/utils/mamba_cache.py

@@ -34,14 +34,18 @@ class BatchMambaCache(MambaCache):
     mlx-lm's BatchGenerator, specifically the `extract` method.
     """
 
-    def __init__(self, left_padding: Optional[List[int]] = None):
+    def __init__(self, left_padding: Optional[List[int]] = None, size: int = 2):
         """
         Initialize BatchMambaCache.
 
         Args:
             left_padding: Amount of left padding for each sequence in batch
+            size: Number of state arrays (default 2 for Mamba models)
         """
-        super().__init__(left_padding=left_padding)
+        if HAS_MAMBA_CACHE:
+            super().__init__(left_padding=left_padding)
+        else:
+            super().__init__(size=size, left_padding=left_padding)
         self._batch_size = len(left_padding) if left_padding else 0
 
     def extract(self, idx: int) -> MambaCache:
@@ -54,7 +58,11 @@ def extract(self, idx: int) -> MambaCache:
         Returns:
             A new MambaCache with the extracted state
         """
-        cache = MambaCache()
+        size = len(self.cache)
+        if HAS_MAMBA_CACHE:
+            cache = MambaCache()
+        else:
+            cache = MambaCache(size=size)
         # Extract the state arrays for this index
         cache.cache = [
             mx.contiguous(c[idx : idx + 1]) if c is not None else None