Vyper Simple Auction

# @version ^0.3.10

beneficiary: public(address)
auctionEndTime: public(uint256)
highestBidder: public(address)
highestBid: public(uint256)
ended: public(bool)

@external
def __init__(_beneficiary: address, _duration: uint256):
    self.beneficiary = _beneficiary
    self.auctionEndTime = block.timestamp + _duration

@external
@payable
def bid():
    assert block.timestamp < self.auctionEndTime, "Auction ended"
    assert msg.value > self.highestBid, "Bid too low"
    if self.highestBid > 0:
        send(self.highestBidder, self.highestBid)
    self.highestBidder = msg.sender
    self.highestBid = msg.value

@external
def endAuction():
    assert block.timestamp >= self.auctionEndTime, "Not yet ended"
    assert not self.ended, "Already ended"
    self.ended = True
    send(self.beneficiary, self.highestBid)