old_contents: class Entity(object):
  	def __init__(self):
  		self.tags = {}
  
  	def setTag(self, tag, value):
  		self.tags[tag] = value
  
  	def unsetTag(self, tag):
  		del self.tags[tag]
  
new_contents: class Entity(object):
  	def __init__(self):
  		self.tags = {}
  
  	def setTag(self, tag, value):
  		self.tags[tag] = value
  
  	def unsetTag(self, tag):
  		del self.tags[tag]
  
  	def getIntProperty(self, tag):
  		ret = self.tags.get(tag, 0)
  		for slot in self.slots:
  			ret += slot.getIntProperty(tag)
  		return ret
  
  	def getBoolProperty(self, tag):
  		if self.tags.get(tag, False):
  			return True
  		for slot in self.slots:
  			if slot.getBoolProperty(tag):
  				return True
  		return
  
subject: Implement Entity.getIntProperty() and getBoolProperty()