docstr: This test should raise `ValueError` because `mean_overlap_var` 
  should be less than `mean_overlap * (1 - mean_overlap)`.
code: def test_get_session_overlap_mean_fail(self, sampler, mean, var):
      """
      This test should raise `ValueError` because `mean_overlap_var`
      should be less than `mean_overlap * (1 - mean_overlap)`.
      """
      sampler.mean_overlap = mean
      sampler.mean_overlap_var = var
      sampler._params = DictConfig(sampler._params)
      with pytest.raises(ValueError) as execinfo:
          sampler.get_session_overlap_mean()
      assert "ValueError" in str(
          execinfo
      ) and "mean_overlap_var" in str(execinfo)
  
imports: import os
  import numpy
  import pytest
  import torch
  from omegaconf import DictConfig
  from nemo.collections.asr.parts.utils.data_simulation_utils import DataAnnotator, SpeechSampler, add_silence_to_alignments, binary_search_alignments, get_cleaned_base_path, get_split_points_in_alignments, normalize_audio, read_noise_manifest
  from nemo.collections.asr.parts.utils.manifest_utils import get_ctm_line
label_desc: Use image node_id 7 for calling the TestSpeechSampler obj's underlying member method code with example usage: obj.test_get_session_overlap_mean_fail(sampler, mean, var) without return types