code: def _check_surf_map(surf_map, n_vertices):
      """Help for plot_surf.
  
      This function checks the dimensions of provided surf_map.
      """
      surf_map_data = load_surf_data(surf_map)
      if surf_map_data.ndim != 1:
          raise ValueError(
              "'surf_map' can only have one dimension "
              f"but has '{surf_map_data.ndim}' dimensions"
          )
      if surf_map_data.shape[0] != n_vertices:
          raise ValueError(
              "The surf_map does not have the same number "
              "of vertices as the mesh."
          )
      return surf_map_data
  
imports: import itertools
  import math
  from collections.abc import Sequence
  from warnings import warn
  import matplotlib
  import matplotlib.pyplot
  import numpy
  from matplotlib import gridspec
  from matplotlib.cm import ScalarMappable
  from matplotlib.colorbar import make_axes
  from matplotlib.colors import LinearSegmentedColormap, Normalize, to_rgba
  from matplotlib.patches import Patch
  from mpl_toolkits.mplot3d.art3d import Poly3DCollection
  from nilearn import image, surface
  from nilearn._utils import check_niimg_3d, compare_version, fill_doc
  from nilearn._utils.helpers import is_kaleido_installed, is_plotly_installed
  from nilearn.plotting.cm import cold_hot, mix_colormaps
  from nilearn.plotting.displays._slicers import _get_cbar_ticks
  from nilearn.plotting.html_surface import get_vertexcolor
  from nilearn.plotting.img_plotting import get_colorbar_and_data_ranges
  from nilearn.plotting.js_plotting_utils import colorscale
  from nilearn.surface import load_surf_data, load_surf_mesh, vol_to_surf
  from nilearn.surface.surface import check_mesh
label_desc: Use image node_id 8 for calling a global function with example usage: _check_surf_map(surf_map, n_vertices) and returns: surf_map_data