Update packages/ltx-core/src/ltx_core/model/transformer/attention.py

packages/ltx-core/src/ltx_core/model/transformer/attention.py

@@ -12,7 +12,10 @@ try:
 except ImportError:
     memory_efficient_attention = None
     
-import flash_attn_interface
+try:
+    import flash_attn_interface
+except ImportError:
+    flash_attn_interface = None
 
 class AttentionCallable(Protocol):
     def __call__(
@@ -120,7 +123,7 @@ class AttentionFunction(Enum):
     def __call__(
         self, q: torch.Tensor, k: torch.Tensor, v: torch.Tensor, heads: int, mask: torch.Tensor | None = None
     ) -> torch.Tensor:
-        if mask is None:
+        if mask is None and flash_attn_interface is not None:
             return FlashAttention3()(q, k, v, heads, mask)
         else:
             return (