code: def forward(self, x, past_kv=None, use_cache=False):
      attn_output, prev_kvs = self.attn(
          self.ln_1(x), past_kv=past_kv, use_cache=use_cache
      )
      x = x + attn_output
      x = x + self.mlp(self.ln_2(x))
      return (x, prev_kvs)
  
imports: import math
  from dataclasses import dataclass
  import torch
  import torch.nn
  from torch.nn import functional
label_desc: Use image node_id 2 for calling the Block obj's underlying member method code with example usage: obj.forward(x, past_kv, use_cache) and returns: x,  prev_kvs