code: def _prune_heads(self, heads_to_prune):
      for layer, heads in heads_to_prune.items():
          self.encoder.block[layer].layer[0].SelfAttention.prune_heads(
              heads
          )
  
imports: from transformers import T5Config, T5PreTrainedModel
  import torch
  from torch import nn
  from copy import deepcopy
  from typing import Optional, Tuple, Union, List
  from itertools import chain
  from transformers.modeling_outputs import TokenClassifierOutput
  from transformers.models.t5.modeling_t5 import T5Stack
  from transformers.utils.model_parallel_utils import get_device_map, assert_device_map
label_desc: Use image node_id 7 for calling the T5ForTokenClassification obj's underlying member method code with example usage: obj._prune_heads(heads_to_prune) without return types