def __init__(self, name, host='127.0.0.1', port=27017):
        self.name = name
        self.host = host
        self.port = port
def get_leafs(self):
		if self.lchild == None and self.rchild == None:
			return [self.leaf]
		else:
			return self.lchild.get_leafs()+self.rchild.get_leafs()