我正在使用Vyper写了一个合约用来获取Uniswap的交易对信息，我可以获取到allPairsLength的信息，但是我把从allPairsLength获取到参数传到getAllPairs里面时每次都是0，而不是获取到的allPairsLength参数，我也不知道我哪里有问题，懂的大佬帮忙看一下，真的很需要帮助

# @version ^0.2

from vyper.interfaces import ERC20

interface UniswapFactory:
    def allPairs(input: uint256) -> address: nonpayable
    def allPairsLength() -> uint256: view

interface UniswapV2Pair:
    def token0() -> address: view
    def token1() -> address: view

UNISWAP_FACTORY: constant(address) = 0x5C69bEe701ef814a2B6a3EDD4B1652CB9cc5aA6f

owner: public(address)

@external
def __init__():
    self.owner = msg.sender

@internal
@view
def getPairsLength() -> uint256:
    """
    @notice From Uniswap factory get last pair length
    @return uint256 pair length
    """
    pl: uint256 = UniswapFactory(UNISWAP_FACTORY).allPairsLength()
    return pl

@external
@view
def getPairsResponse() -> Bytes[128]:
    """
    @notice From Uniswap factory get new pair address 
    @return address pairAddress 
    """

    _response: Bytes[128] = raw_call(
        UNISWAP_FACTORY,
        concat(
            method_id("allPairs(uint256)"),
            convert(self.getPairsLength(), bytes32)
        ),
        max_outsize=128,
        is_static_call=True
    )
    return _response