code: def __getitem__(self, idx):
      # The simple implementation is just a single "return self.ndarray[idx]"
      # The following is for demo and testing purpose.
      if isinstance(idx, numbers.Integral):
          return self.ndarray[idx]
      elif isinstance(idx, slice):
          if not (idx.step is None or idx.step == 1):
              raise NotImplementedError(
                  "No need to implement, caller will not set step by now"
              )
          return self.ndarray[idx.start : idx.stop]
      elif isinstance(idx, list):
          return self.ndarray[idx]
      else:
          raise TypeError(
              f"Sequence Index must be an integer/list/slice, got {type(idx).__name__}"
          )
  
imports: import filecmp
  import numbers
  import re
  from copy import deepcopy
  from os import getenv
  from pathlib import Path
  import numpy
  import pytest
  from scipy import sparse
  from sklearn.datasets import dump_svmlight_file, load_svmlight_file
  from sklearn.model_selection import train_test_split
  import lightgbm
  from lightgbm.compat import PANDAS_INSTALLED, pd_DataFrame, pd_Series
  from .utils import dummy_obj, load_breast_cancer, mse_obj, np_assert_array_equal
label_desc: Use image node_id 2 for calling the NumpySequence obj's underlying member method code with example usage: obj.__getitem__(idx) and returns: self, self, self