Codacy Small Bug Fixes:

- cleaned up imports
- cleaned up some code
- added docstrings

examples/problems/poisson.py

@@ -1,3 +1,4 @@
+""" Poisson equation example. """
 import numpy as np
 import torch
 
@@ -46,8 +47,9 @@ class Poisson(SpatialProblem):
     # real poisson solution
     def poisson_sol(self, pts):
         return -(
-            torch.sin(pts.extract(['x'])*torch.pi)*
+            torch.sin(pts.extract(['x'])*torch.pi) *
             torch.sin(pts.extract(['y'])*torch.pi)
         )/(2*torch.pi**2)
+        # return -(np.sin(x*np.pi)*np.sin(y*np.pi))/(2*np.pi**2)
 
     truth_solution = poisson_sol