please explain the following code part of adding x and y

[VinACE]

please explain the following code part of adding x and y
vasnet_model.py
class VASNet(nn.Module):
.....
def forward(self, x, seq_len):

    m = x.shape[2] # Feature size

    # Place the video frames to the batch dimension to allow for batch arithm. operations.
    # Assumes input batch size = 1.
    x = x.view(-1, m)
    y, att_weights_ = self.att(x)

    y = y + x # -- what is the reason behind this step please explain,

[Pager07]

residual link. It's in the diagram. Please read the paper