Fixed default argument for backend

Author: fonnesbeck

python/nutpie/compile_pymc.py

@@ -354,7 +354,7 @@ def expand(x, **shared):
 def compile_pymc_model(
     model: "pm.Model",
     *,
-    backend: Literal["numba", "jax"] = "numba",
+    backend: Literal["numba", "jax"] | None = None,
     gradient_backend: Literal["pytensor", "jax"] | None = None,
     **kwargs,
 ) -> CompiledModel: