code: def step(self, x, state, **kwargs):
      if self.stride > 1 or self.expand > 1:
          raise NotImplementedError
      return x, state
  
imports: import torch
  import torch.nn.functional
  from einops import rearrange, reduce, repeat
  from torch import nn
  from espnet2.asr.state_spaces.base import SequenceModule
  from espnet2.asr.state_spaces.components import LinearActivation
label_desc: Use image node_id 3 for calling the DownSample obj's underlying member method code with example usage: obj.step(x, state) and returns: x,  state