Snapshot of `add_layer` method from https://gist.github.com/schaunwheeler/9a98d8bee5f039e9872c76fb24a6e69c

method_add_layer.py

"""
Code described in Medium post https://medium.com/@schaun.wheeler/codify-your-workflow-377f5f8bf4c3
Copyright (c) 2018 Valassis Digital under the terms of the BSD 3-Clause license.
"""

def add_layer(self, source_label, bokeh_model, tooltips=None, **kwargs):
     
    if self.plot is None:
        raise AssertionError('self.plot is null; call `self.prepare_plot`.')
     
    if 'color' in kwargs.keys():
        color = kwargs.pop('color')
        kwargs['fill_color'] = color
        kwargs['line_color'] = color
 
    if 'alpha' in kwargs.keys():
        alpha = kwargs.pop('alpha')
        kwargs['fill_alpha'] = alpha
        kwargs['line_alpha'] = alpha
             
    try:
        model_object = bokeh_model(xs='x_coords', ys='y_coords', name=source_label, **kwargs)
    except AttributeError:
        model_object = bokeh_model(x='x_coords_point', y='y_coords_point', name=source_label, **kwargs)
        if not all(c in self.sources[source_label].column_names for c in ['x_coord_point', 'y_coord_point']):
            self.sources[source_label].data['x_coords_point'] = [mean(x) for x in self.sources[source_label].data['x_coords']]
            self.sources[source_label].data['y_coords_point'] = [mean(x) for x in self.sources[source_label].data['y_coords']]
            self.sources[source_label].column_names.extend(['x_coords_point', 'y_coords_point'])
         
    rend = self.plot.add_glyph(self.sources[source_label], model_object)
     
    if tooltips is not None:
        self.plot.add_tools(HoverTool(tooltips=tooltips, renderers=[rend]))