Make EgoSpeak Mamba dependency optional

third_party/EgoSpeak/MiniROAD/model/model_builder.py

@@ -1,9 +1,37 @@
 __all__ = ['build_model']
 
+import importlib
+
 from utils import Registry
 
 META_ARCHITECTURES = Registry()
+_MAMBA_MODELS = frozenset({"Mamba", "MambaA"})
+
+
+def _load_optional_architecture(model_name):
+    if model_name not in _MAMBA_MODELS or model_name in META_ARCHITECTURES:
+        return
+
+    try:
+        importlib.import_module(".mamba", package=__package__)
+    except ModuleNotFoundError as error:
+        missing_package = error.name or "mamba_ssm"
+        raise ModuleNotFoundError(
+            f"Model {model_name!r} requires the optional Mamba backend "
+            f"(missing package: {missing_package!r}). Install "
+            "requirements-mamba.txt, or use MiniROAD/MiniROADA without it."
+        ) from error
+
 
 def build_model(cfg, device=None):
-    model = META_ARCHITECTURES[cfg["model"]](cfg)
-    return model.to(device)
+    model_name = cfg["model"]
+    _load_optional_architecture(model_name)
+
+    if model_name not in META_ARCHITECTURES:
+        available = ", ".join(sorted(META_ARCHITECTURES))
+        raise KeyError(
+            f"Unknown model {model_name!r}. Available architectures: {available}"
+        )
+
+    model = META_ARCHITECTURES[model_name](cfg)
+    return model.to(device)