[Loss function] Adding the loss function

losses/RMSLE.py

+import torch.nn as nn
+
+class RMSLELoss(nn.Module):
+    def __init__(self):
+        super().__init__()
+        self.mse = nn.MSELoss()
+        
+    def forward(self, pred, actual):
+        return torch.sqrt(self.mse(torch.log(pred + 1), torch.log(actual + 1)))
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