bokeh.palettes.Inferno

def histogram_plot(nx, ny, x, source, xlo=None, xhi=None, nsub=5, output_backend=DEFAULT_BACKEND):
    if not present(source, x): return None
    xlo, xhi = source[x].min() if xlo is None else xlo, source[x].max() if xhi is None else xhi
    bins = pd.interval_range(start=xlo, end=xhi, periods=nsub * (xhi - xlo), closed='left')
    c = [palettes.Inferno[int(xhi - xlo + 1)][int(b.left - xlo)] for b in bins]
    hrz_categorized = pd.cut(source[x], bins)
    counts = hrz_categorized.groupby(hrz_categorized).count()
    f = figure(output_backend=output_backend, plot_width=nx, plot_height=ny, x_range=Range1d(start=xlo, end=xhi),
               x_axis_label=x)
    f.quad(left=counts.index.categories.left, right=counts.index.categories.right, top=counts, bottom=0,
           color=c, fill_alpha=0.2)
    f.toolbar_location = None
    f.yaxis.visible = False
    return f


def add_route(f, source, color='black', line_dash='solid'):