why the check_palin() function return 'None', not True or False

gistfile1.py

def check_palin(lister):
	if  len(lister) <= 1 :
		print 'True'
		return True 
	else:
		if lister[0] == lister[-1]:
			lister.pop()
			del lister[0]
			check_palin(lister)
		else:
			print  'False'
			return False 

def remove_white(string):
	a = []
	for i in string:
		if i != ' ':
			a.append(i)
	return a


print check_palin(remove_white('y - akay'))

explain