code: def forward(self, seq, mask):
      # seq: (N, C, L)
      # mask: (N, L)
      seq_mask = torch.unsqueeze(mask, 2)
      seq_mask = torch.transpose(
          seq_mask.repeat(1, 1, seq.size()[1]), 1, 2
      )
      return seq.where(torch.eq(seq_mask, 1), torch.zeros_like(seq))
  
imports: import torch
  import torch.nn.functional
  from torch import nn
  from utils import get_length, INF
label_desc: Use image node_id 1 for calling the Mask obj's underlying member method code with example usage: obj.forward(seq, mask) and returns: seq