code: def _get_text(self, idx: int) -> np.ndarray:
      np_gen = np.random.default_rng(seed=(self.seed + idx))
      return np_gen.integers(
          self.vocab_size, size=[self.seq_length], dtype=np.int64
      )
  
imports: import os
  import time
  import numpy
  import torch
  from omegaconf.dictconfig import DictConfig
  from nemo.collections.nlp.data.language_modeling.megatron.base_dataset_utils import get_datasets_weights_and_num_samples, get_train_valid_test_split_
  from nemo.collections.nlp.data.language_modeling.megatron.blendable_dataset import BlendableDataset
  from nemo.collections.nlp.data.language_modeling.megatron.indexed_dataset import deallocate_indexed_dataset_memory
  from nemo.collections.nlp.data.language_modeling.megatron.indexed_dataset import make_dataset
  from nemo.core import Dataset
  from nemo.utils import logging
label_desc: Use image node_id 3 for calling the MockGPTDataset obj's underlying member method code with example usage: obj._get_text(idx) and returns: np_gen