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// contracts/delegator.sol
// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;
import "@openzeppelin/contracts/interfaces/IERC721.sol";
import "@openzeppelin/contracts/interfaces/IERC20.sol";
import "@openzeppelin/contracts/token/ERC20/utils/SafeERC20.sol";
import "@openzeppelin/contracts/utils/cryptography/ECDSA.sol";
import "@openzeppelin/contracts/utils/math/SafeCast.sol";
/// @title Harpie Vault Contract
/// @author https://harpie.io, 2022
/// @notice This contract is designed to hold ERC20s and ERC721s from user wallets and allow only them to withdraw.
/// Users will have to pay a designated fee in order to withdraw their ERC20s and ERC721s.
/// In case we need to reduce fees for each user, we have reduceFee functions we can call. 
contract Vault {
    using ECDSA for bytes32;
    using SafeCast for uint128;
    using SafeCast for uint256;
    /// @dev We use safeERC20 for noncompliant ERC20s
    using SafeERC20 for IERC20;
    /// @dev This struct defines the amount of an ERC20 stored, and the fee required to withdraw
    struct erc20Struct {
        uint128 amountStored;
        uint128 fee;
    }
    /// @dev This struct defines if an ERC721 id is stored, and the fee required to withdraw
    struct erc721Struct {
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