code: def expected_vmin_vmax(values, vmax, vmin):
      """Returns expected vmin and vmax."""
      if vmax is None:
          return (min(values), max(values))
      if min(values) < 0:
          return (-vmax, vmax)
      return (min(values), vmax) if vmin is None else (vmin, vmax)
  
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 8 for calling a global function with example usage: expected_vmin_vmax(values, vmax, vmin) and returns: unknown, min,  max, unknown,  vmax