     require(_newYieldSource.depositToken() == yieldSource.depositToken(), "`SwappableYieldSource`/different-deposit-token");

function initialize( IYieldSource _yieldSource, uint8 _decimals, string calldata _symbol, string calldata _name, address _owner) public initializer returns (bool) {
    _requireYieldSource(_yieldSource);

 function _requireYieldSource(IYieldSource _yieldSource) internal view {
    require(address(_yieldSource) != address(0), "SwappableYieldSource/yieldSource-not-zero-address");
    (, bytes memory depositTokenAddressData) = address(_yieldSource).staticcall(abi.encode(_yieldSource.depositToken.selector));
    bool isInvalidYieldSource;
    if (depositTokenAddressData.length > 0) {
      (address depositTokenAddress) = abi.decode(depositTokenAddressData, (address));
      isInvalidYieldSource = depositTokenAddress != address(0);
    }
    require(isInvalidYieldSource, "SwappableYieldSource/invalid-yield-source");
  }

 function _setYieldSource(IYieldSource _newYieldSource) internal {
    _requireDifferentYieldSource(_newYieldSource);
    require(_newYieldSource.depositToken() == yieldSource.depositToken(), "SwappableYieldSource/different-deposit-token");
...

 function _requireDifferentYieldSource(IYieldSource _yieldSource) internal view {
    require(address(_yieldSource) != address(yieldSource), "SwappableYieldSource/same-yield-source");
  }
_requireYieldSource(_newYieldSource);
