code: def _allocate_buffer(self):
      assert self.current_buffer_index == INVALID_BUFFER_INDEX
      assert len(self.all_buffers) > 0
      assert len(self.free_buffer_index) > 0
      self.current_buffer_index = self.free_buffer_index[-1]
      self.free_buffer_index = self.free_buffer_index[:-1]
  
imports: import torch
  from deepspeed import comm
  from deepspeed.utils.logging import logger
  from deepspeed.runtime.swap_tensor.utils import swap_out_tensors, SwapBuffer
label_desc: Use image node_id 11 for calling the AsyncTensorSwapper obj's underlying member method code with example usage: obj._allocate_buffer() without return types