code: def mask_input(self, x, lens):
      max_len = x.size(2)
      mask = self.lens[:max_len].unsqueeze(0).to(
          lens.device
      ) < lens.unsqueeze(1)
      x = x * mask.unsqueeze(1).to(device=x.device)
      return x
  
imports: import math
  from typing import Callable, Iterable, List, Optional, Tuple
  import torch
  import torch.nn
  import torch.nn.functional
  from torch import Tensor
  from torch.nn.init import _calculate_correct_fan
  from torch.nn.modules.utils import _single
  from nemo.collections.common.parts.utils import activation_registry
  from nemo.core.classes.mixins import AccessMixin
  from nemo.core.classes.mixins.adapter_mixins import AdapterModuleMixin
  from nemo.utils import logging
label_desc: Use image node_id 5 for calling the MaskedConv1d obj's underlying member method code with example usage: obj.mask_input(x, lens) and returns: x