Refactoring code

pina/deep_feed_forward.py

@@ -1,5 +1,3 @@
-
-from .problem import Problem
 import torch
 import torch.nn as nn
 import numpy as np
@@ -12,18 +10,18 @@ from pina.label_tensor import LabelTensor
 
 class DeepFeedForward(torch.nn.Module):
 
-    def __init__(self, 
-            inner_size=20, 
-            n_layers=2, 
-            func=nn.Tanh, 
-            input_variables=None, 
-            output_variables=None, 
-            layers=None, 
+    def __init__(self,
+            inner_size=20,
+            n_layers=2,
+            func=nn.Tanh,
+            input_variables=None,
+            output_variables=None,
+            layers=None,
             extra_features=None):
         '''
         '''
         super(DeepFeedForward, self).__init__()
-        
+
         if extra_features is None:
             extra_features = []
         self.extra_features = nn.Sequential(*extra_features)
@@ -48,7 +46,7 @@ class DeepFeedForward(torch.nn.Module):
         self.layers = []
         for i in range(len(tmp_layers)-1):
             self.layers.append(nn.Linear(tmp_layers[i], tmp_layers[i+1]))
-            
+
 
 
         if isinstance(func, list):