Fix Codacy Warnings (#477)

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Co-authored-by: Dario Coscia <dariocos99@gmail.com>

pina/model/low_rank_neural_operator.py

@@ -1,7 +1,7 @@
 """Module LowRank Neural Operator."""
 
 import torch
-from torch import nn, cat
+from torch import nn
 
 from ..utils import check_consistency
 
@@ -145,4 +145,4 @@ class LowRankNeuralOperator(KernelNeuralOperator):
         for module in self._integral_kernels:
             x = module(x, coords)
         # projecting
-        return self._projection_operator(cat((x, coords), dim=-1))
+        return self._projection_operator(torch.cat((x, coords), dim=-1))