Matplotlib - отсечки для нескольких графиков

import matplotlib.pyplot as my_graph
import matplotlib.dates as mdates
def several_tag(tags):
	mmin=[]
	mmax=[]
	current_db=r.hget('db_id', 'value')
	data=db_arch[current_db]

	for ctag in tags:
		vals=[]
		times=[]
		tag_values=data.find({'tagname':ctag},{'value':1,'time':1,'_id':0})
		for tag in tag_values:
			try:
				vals.append(round(float(tag['value']),2))
			except:
				vals.append(0)
			times.append(datetime.fromtimestamp(tag['time']))

		mmin.append(min(vals))
		mmax.append(max(vals))
		my_graph.ylim(min(mmin)-5,max(mmax)+5)

		my_graph.plot(times, vals)

		axes = my_graph.subplot(1, 1, 1)
		axes.xaxis.set_major_formatter(mdates.DateFormatter("%H:%M:%S"))
		locator=mdates.ticker.FixedLocator([mdates.date2num(times[vals.index(min(vals))]),mdates.date2num(times[vals.index(max(vals))])])
		axes.xaxis.set_major_locator(locator)

		my_graph.xticks(size="xx-small", color="gray")

		my_graph.annotate('max: %s' % max(vals), size="x-small", color="red", xy=(mdates.date2num(times[vals.index(max(vals))]), max(vals)), xycoords='data', xytext=(10, 10), textcoords='offset points', arrowprops=dict(arrowstyle='-|>'))
		my_graph.annotate('min: %s' % min(vals), size="x-small", color=(0.4, 0.5, 0.3), xy=(mdates.date2num(times[vals.index(min(vals))]), min(vals)), xycoords='data', xytext=(15, -15), textcoords='offset points', arrowprops=dict(arrowstyle='-|>'))

		my_graph.grid(True)

	my_graph.savefig(r'1.png', transparent=True)


several_tag(['MKA50GE004ZQ_V', 'MKA50GE003ZQ_V'])