code: def guide_colorbar(barwidth=None, barheight=None, nbin=None):
      """
      Continuous color bar guide.
  
      Parameters
      ----------
      barwidth : float
          Color bar width in px.
      barheight : float
          Color bar height in px.
      nbin : int
          Number of bins in color bar.
  
      Returns
      -------
      `FeatureSpec`
          Color guide specification.
  
      Notes
      -----
      Color bar guide shows continuous color scales mapped onto values.
      Color bar is available with scale_fill and scale_color.
  
      Examples
      --------
      .. jupyter-execute::
          :linenos:
          :emphasize-lines: 12
  
          import numpy as np
          from lets_plot import *
          LetsPlot.setup_html()
          n = 50
          np.random.seed(42)
          x = np.random.uniform(size=n)
          y = np.random.uniform(size=n)
          v = np.random.normal(size=n)
          ggplot({'x': x, 'y': y, 'v': v}, aes('x', 'y')) + \\
              geom_point(aes(fill='v'), size=4, shape=21, color='black') + \\
              scale_fill_gradient2(low='red', mid='yellow', high='blue', \\
                                   guide=guide_colorbar(nbin=8, barwidth=10))
  
      """
      return _guide("colorbar", **locals())
  
imports: from .core import FeatureSpec
label_desc: Use image node_id 2 for calling a global function with example usage: guide_colorbar(barwidth, barheight, nbin) and returns: _guide