code: def test_conversion():
      brifti_obj = nib.load(data_file)
      vol_img = as_volume_img(data_file)
      assert as_volume_img(vol_img) == vol_img
      assert as_volume_img(brifti_obj) == vol_img
  
file_path: nipy/nipy/labs/datasets/tests/test_converters.py
imports: import os
  import tempfile
  import nibabel
  import pytest
  from ..None import as_volume_img, save
label_desc: Use image node_id 1 for calling a global function with example usage: test_conversion() without return types