code: def _unpack(self, x, f_len, g_len):
      batch_offset = torch.cumsum(f_len * g_len, dim=0)
      x_unpacked = torch.zeros_like(self.h_grad, dtype=torch.uint8)
      B = self.h_grad.size(0)
      H = self.h_grad.size(-1)
      for b in range(B):
          my_batch_offset = 0 if b == 0 else batch_offset[b - 1]
          my_f_len = f_len[b]
          my_g_len = g_len[b]
          for t in range(my_f_len):
              x_unpacked[b, t, :my_g_len] = x[
                  my_batch_offset
                  + t * my_g_len : my_batch_offset
                  + t * my_g_len
                  + my_g_len
              ]
      return x_unpacked
  
imports: import unittest
  import torch
label_desc: Use image node_id 4 for calling the TransducerJointTest obj's underlying member method code with example usage: obj._unpack(x, f_len, g_len) and returns: x_unpacked