From 9cfecec415785562c53f6b47eab38758727a1b9c Mon Sep 17 00:00:00 2001
From: "Robert P. Goldman" <rpgoldman@goldman-tribe.org>
Date: Mon, 6 May 2019 10:26:28 -0500
Subject: [PATCH] Remove unused powerset function.

This function was rendered unnecessary by the revision of the _get_ancestors() method.
---
 pymc3/model_graph.py | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/pymc3/model_graph.py b/pymc3/model_graph.py
index 512b529ae5c..743f4142c08 100644
--- a/pymc3/model_graph.py
+++ b/pymc3/model_graph.py
@@ -12,7 +12,6 @@
 # of variables in a model.
 RV = Tensor
 
-
 class ModelGraph:
     def __init__(self, model):
         self.model = model
@@ -35,10 +34,10 @@ def _get_ancestors(self, var, func) -> MutableSet[RV]:
         """
 
         # this contains all of the variables in the model EXCEPT var...
-        vars = set(self.var_list)
+        vars: MutableSet[RV] = set(self.var_list)
         vars.remove(var)
-
-        blockers = set()
+        
+        blockers: MutableSet[RV] = set()
         retval = set()
         def _expand(node) -> Optional[Iterator[Tensor]]:
             if node in blockers: