Update pymc_experimental/model/marginal_model.py

Co-authored-by: Ricardo Vieira <[email protected]>

Author: zaxtax

pymc_experimental/model/marginal_model.py

@@ -234,7 +234,7 @@ def clone(self):
         return m
 
     def marginalize(
-        self, rvs_to_marginalize: Union[TensorVariable, Sequence[TensorVariable], Sequence[str]]
+        self, rvs_to_marginalize: Union[TensorVariable, str, Sequence[TensorVariable], Sequence[str]]
     ):
         if not isinstance(rvs_to_marginalize, Sequence):
             rvs_to_marginalize = (rvs_to_marginalize,)