code: def _perform_getitem(cls, dataset, index):
      raise NotImplementedError()
  
imports: import sys
  import warnings
  import numpy
  import param
  from ..None import util
  from ..element import Element
  from ..ndmapping import NdMapping
  from .util import finite_range
label_desc: Use image node_id 3 for calling the Accessor obj's underlying member method code with example usage: obj._perform_getitem(cls, dataset, index) without return types