code: def test_colorscale_no_threshold():
      """Test colorscale with no thresholding."""
      values = np.linspace(-13, -1.5, 20)
      colors = colorscale("jet", values, None)
      check_colors(colors["colors"])
      assert (colors["vmin"], colors["vmax"]) == (-13, 13)
      assert colors["cmap"].N == 256
      assert (colors["norm"].vmax, colors["norm"].vmin) == (13, -13)
      assert colors["abs_threshold"] is None
  
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 4 for calling a global function with example usage: test_colorscale_no_threshold() without return types