diff --git a/pymc_extras/prior.py b/pymc_extras/prior.py
index 64def0c2..a4f5ffa4 100644
--- a/pymc_extras/prior.py
+++ b/pymc_extras/prior.py
@@ -335,6 +335,7 @@ class VariableFactory(Protocol):
 
         class PowerSumDistribution:
             """Create a distribution that is the sum of powers of a base distribution."""
+
             def __init__(self, distribution: VariableFactory, n: int):
                 self.distribution = distribution
                 self.n = n
@@ -345,7 +346,12 @@ def dims(self):
 
             def create_variable(self, name: str) -> "TensorVariable":
                 raw = self.distribution.create_variable(f"{name}_raw")
-                return pm.Deterministic(name, pt.sum([raw ** n for n in range(1, self.n + 1)], axis=0), dims=self.dims,)
+                return pm.Deterministic(
+                    name,
+                    pt.sum([raw**n for n in range(1, self.n + 1)], axis=0),
+                    dims=self.dims,
+                )
+
 
         cubic = PowerSumDistribution(Prior("Normal"), n=3)
         samples = sample_prior(cubic)
@@ -533,8 +539,10 @@ class Prior:
 
         from pymc_extras.prior import register_tensor_transform
 
+
         def custom_transform(x):
-            return x ** 2
+            return x**2
+
 
         register_tensor_transform("square", custom_transform)