class X(object):
	def __init__(self):
		self._x = []
		self._y = 0

	def setX(self, x):
		self._x = x

	def __str__(self):
		return self._x

class Z(object):
	def __init__(self):
		self._a = 0
		self._b = 0

class Y(X, Z):
	def __init__(self, x, y):
		self._y = y
		super(Y, self).__init__()

	def __str__(self):
		return "Hola mundo"