[Hybrid] Added supports_mamba_prefix_caching Protocol (#27339)

Signed-off-by: asafg <39553475+Josephasafg@users.noreply.github.com>

vllm/model_executor/models/interfaces.py

@@ -697,6 +697,34 @@ def has_noops(
     return getattr(model, "has_noops", False)
 
 
+@runtime_checkable
+class SupportsMambaPrefixCaching(Protocol):
+    """The interface for models whose mamba layers support prefix caching.
+
+    This is currently experimental.
+    """
+
+    supports_mamba_prefix_caching: ClassVar[Literal[True]] = True
+
+
+@overload
+def supports_mamba_prefix_caching(
+    model: object,
+) -> TypeIs[SupportsMambaPrefixCaching]: ...
+
+
+@overload
+def supports_mamba_prefix_caching(
+    model: type[object],
+) -> TypeIs[type[SupportsMambaPrefixCaching]]: ...
+
+
+def supports_mamba_prefix_caching(
+    model: type[object] | object,
+) -> TypeIs[type[SupportsMambaPrefixCaching]] | TypeIs[SupportsMambaPrefixCaching]:
+    return getattr(model, "supports_mamba_prefix_caching", False)
+
+
 @runtime_checkable
 class SupportsCrossEncoding(Protocol):
     """The interface required for all models that support cross encoding."""