code: def test_colorscale_threshold(threshold, expected_abs_threshold):
      """Test colorscale with different threshold values."""
      colors = colorscale(
          "jet", np.linspace(-13, -1.5, 20), threshold=threshold
      )
      _, cstring = check_colors(colors["colors"])
      assert cstring[50] == "rgb(127, 127, 127)"
      assert (colors["vmin"], colors["vmax"]) == (-13, 13)
      assert colors["cmap"].N == 256
      assert (colors["norm"].vmax, colors["norm"].vmin) == (13, -13)
      assert np.allclose(
          colors["abs_threshold"], expected_abs_threshold, 2
      )
      assert colors["symmetric_cmap"]
  
imports: import base64
  import os
  import re
  import tempfile
  import numpy
  import pytest
  from nilearn.datasets import fetch_surf_fsaverage
  from nilearn.plotting.js_plotting_utils import add_js_lib, colorscale, decode, encode, get_html_template, mesh_to_plotly, to_color_strings
  from nilearn.surface import load_surf_mesh
label_desc: Use image node_id 6 for calling a global function with example usage: test_colorscale_threshold(threshold, expected_abs_threshold) without return types