class ReplayBuffer(object):
	def __init__(self, conf):
		'''
		Initialize a replay buffer with parameters in conf.
		'''
		pass

	def add(self, data, priority):
		'''
		Add a data with priority = priority to replay buffer.
		'''
		pass

	def update_priority(self, indices, priorities):
		'''
		Update the data's priority whose indices = indices.
		For proportional replay buffer, the priority is the priority.
		For rank based replay buffer, the priorities parameter will be the delta used to update the priority.
		'''
		pass

	def reset_alpha(self, alpha):
		'''
		This function only works for proportional replay buffer.
		This function resets alpha.
		'''
		pass

	def sample(self, conf):
		'''
		Sample from replay buffer with parameters in conf.
		'''
		pass

	def rebalance(self):
		'''
		This is for rank based priority replay buffer, which is used to rebalance the sum tree of the priority queue.
		'''
		pass