code: def get_num_batches(self, instances: Sequence[Instance]) -> int:
      raise NotImplementedError
  
imports: from typing import List, Iterable, Sequence, Optional
  from allennlp.common.registrable import Registrable
  from allennlp.data.instance import Instance
label_desc: Use image node_id 2 for calling the BatchSampler obj's underlying member method code with example usage: obj.get_num_batches(instances) without return types