Update DiagonalSubtensor.grad to don't return None.

theanoconv3d2d/conv3d2d.py

+from theano.gradient import DisconnectedType
 from theano.gof import Op, Apply
 from theano import tensor
 
+
 def get_diagonal_subtensor_view(x, i0, i1):
     if x.shape[i0] < x.shape[i1]:
         raise NotImplementedError('is this allowed?')
@@ -31,10 +33,16 @@ class DiagonalSubtensor(Op):
             output_storage[0][0] = xview
         else:
             output_storage[0][0] = xview.copy()
+
     def grad(self, inputs, g_outputs):
         z = tensor.zeros_like(inputs[0])
         gx = inc_diagonal_subtensor(z, inputs[1], inputs[2], g_outputs[0])
-        return [gx] + [None] * (len(inputs)-1)
+        return [gx, DisconnectedType()(), DisconnectedType()()]
+
+    def connection_pattern(self, node):
+        rval = [[True], [False], [False]]
+        return rval
+
 diagonal_subtensor = DiagonalSubtensor(False)
 
 class IncDiagonalSubtensor(Op):