code: def _get_colormapper(
      self,
      eldim,
      element,
      ranges,
      style,
      factors=None,
      colors=None,
      group=None,
      name="color_mapper",
  ):
      cmapper = super()._get_colormapper(
          eldim,
          element,
          ranges,
          style,
          factors=factors,
          colors=colors,
          group=group,
          name=name,
      )
      num_elements = len(element.vdims)
      step_size = len(cmapper.palette) // num_elements
      indices = np.arange(num_elements) * step_size
      cmapper.palette = np.array(cmapper.palette)[indices].tolist()
      return cmapper
  
imports: import sys
  import numpy
  import param
  from bokeh.models import CustomJSHover, DatetimeAxis
  from ...core.util import cartesian_product, dimension_sanitizer, isfinite
  from ...element import Raster
  from ..util import categorical_legend
  from .chart import PointPlot
  from .element import ColorbarPlot, LegendPlot
  from .selection import BokehOverlaySelectionDisplay
  from .styles import base_properties, fill_properties, line_properties, mpl_to_bokeh
  from .util import bokeh33, bokeh34, colormesh
label_desc: Use image node_id 2 for calling the ImageStackPlot obj's underlying member method code with example usage: obj._get_colormapper(eldim, element, ranges, style, factors, colors, group, name) and returns: cmapper