code: def test_write_read_grayscale_uint8_png(tmpdir):
      filename = tmpdir / "grayscale_uint8.png"
      img_data = np.arange(256, dtype=np.uint8).reshape((16, 16, 1))
      file_io.write_png(img_data, filename)
      img_data_recovered = file_io.read_png(filename)
      np.testing.assert_array_equal(img_data, img_data_recovered)
  
file_path: kubric/test/test_fileio.py
imports: import numpy
  import pytest
  from kubric import file_io
label_desc: Use image node_id 1 for calling a global function with example usage: test_write_read_grayscale_uint8_png(tmpdir) without return types