code: def init_mems(self, x):
      if self.mem_len > 0:
          mems = []
          for i in range(self.n_layer + 1):
              empty = torch.empty(0, dtype=x.dtype, device=x.device)
              mems.append(empty)
  
          return mems
      else:
          return None
  
imports: import sys
  import math
  import functools
  import numpy
  import torch
  import torch.nn
  import torch.nn.functional
  from proj_adaptive_softmax import ProjectedAdaptiveLogSoftmax, Projection
  from log_uniform_sampler import LogUniformSampler, sample_logits
  from fmoe import FMoETransformerMLP
label_desc: Use image node_id 5 for calling the MemTransformerLM obj's underlying member method code with example usage: obj.init_mems(x) and returns: mems, None