How to control the colorbar and show it horizontally in matplotlib?

Question

I have a grid and in each cell of the grid I plot circles where the circle has a color that is linked to a colorbar.

However colorbar is shown automatically in the right hand side of the plot.

How to control the colorbar and show it below the circles as horizontal?

The code below generates the given figure.

import matplotlib
import numpy as np
import os
import matplotlib as mpl
from matplotlib.colors import Normalize
import matplotlib.cm as matplotlib_cm
from matplotlib import pyplot as plt


jobname="DEBUG"
row_list=['row1', 'row2', 'row3']
column_list=[2]
maxProcessiveGroupLength=2
index = column_list.index(maxProcessiveGroupLength)

plot1, panel1 = plt.subplots(figsize=(20+1.5*len(column_list), 10+1.5*len(row_list)))
plt.rc('axes', edgecolor='lightgray')

#make aspect ratio square
panel1.set_aspect(1.0)
panel1.text(0.1, 1.2, jobname,horizontalalignment='center', verticalalignment='top', fontsize=60, fontweight='bold', fontname='Arial',transform=panel1.transAxes)

if (len(column_list) > 1):
    panel1.set_xlim([1, index + 1])
    panel1.set_xticks(np.arange(0, index + 2, 1))
else:
    panel1.set_xlim([0, len(column_list)])
    panel1.set_xticks(np.arange(0, len(column_list)+1, 1))

if (len(row_list) > 1):
    panel1.set_ylim([1, len(row_list)])
else:
    panel1.set_ylim([0, len(row_list)])

panel1.set_yticks(np.arange(0, len(row_list) + 1, 1))

panel1.set_facecolor('white')
panel1.grid(color='black')

for edge, spine in panel1.spines.items():
    spine.set_visible(True)
    spine.set_color('black')

xlabels = None
if (index is not None):
    xlabels = column_list[0:index + 1]
ylabels = row_list

cmap = matplotlib_cm.get_cmap('Blues')  # Looks better
v_min = 2
v_max = 20
norm = Normalize(v_min, v_max)
bounds = np.arange(v_min, v_max+1, 2)

# Plot the circles with color
for row_index, row in enumerate(row_list):
    for column_index, processive_group_length in enumerate(column_list):
        radius=0.35
        color=10+column_index*3+row_index*3
        circle = plt.Circle((column_index + 0.5, row_index + 0.5), radius,color=cmap(norm(color)), fill=True)
        panel1.add_patch(circle)

# Vertical Colorbar
# Used for scatter plot
x = []
y = []
c = []

for row_index, processiveGroupLength in enumerate(row_list):
    x.append(row_index)
    y.append(row_index)
    c.append(0.5)

# This code defines the ticks on the color bar
# plot the scatter plot
sc = plt.scatter(x, y, s=0, c=c, cmap=cmap, vmin=v_min, vmax=v_max, edgecolors='black')
cb = plt.colorbar(sc)  # this works because of the scatter

cb.ax.set_ylabel("colorbar label", fontsize=50, labelpad=25)

# common for horizontal colorbar and vertical colorbar
cbax = cb.ax
cbax.tick_params(labelsize=40)
text_x = cbax.xaxis.label
text_y = cbax.yaxis.label
font = mpl.font_manager.FontProperties(size=40)
text_x.set_font_properties(font)
text_y.set_font_properties(font)

# CODE GOES HERE TO CENTER X-AXIS LABELS...
panel1.set_xticklabels([])
mticks = panel1.get_xticks()
panel1.set_xticks((mticks[:-1] + mticks[1:]) / 2, minor=True)
panel1.tick_params(axis='x', which='minor', length=0, labelsize=50)

if xlabels is not None:
    panel1.set_xticklabels(xlabels,minor=True)

panel1.xaxis.set_ticks_position('top')

plt.tick_params(
    axis='x',  # changes apply to the x-axis
    which='major',  # both major and minor ticks are affected
    bottom=False,  # ticks along the bottom edge are off
    top=False)  # labels along the bottom edge are off


# CODE GOES HERE TO CENTER Y-AXIS LABELS...
panel1.set_yticklabels([])
mticks = panel1.get_yticks()
panel1.set_yticks((mticks[:-1] + mticks[1:]) / 2, minor=True)
panel1.tick_params(axis='y', which='minor', length=0, labelsize=50)
panel1.set_yticklabels(ylabels, minor=True)  # fontsize

plt.tick_params(
    axis='y',  # changes apply to the x-axis
    which='major',  # both major and minor ticks are affected
    left=False)  # labels along the bottom edge are off


plt.show()