/*
     * @notice Overrides the msgSender to enable delegation message signing.
     * @returns address - The account whose authority is being acted on.
     */
    function _msgSender()
        internal
        view
        virtual
        override(DelegatableCore)
        returns (address sender)
    {
        if (msg.sender == address(this)) {
            bytes memory array = msg.data;
            uint256 index = msg.data.length;
            assembly {
                sender := and(
                    mload(add(array, index)),
                    0xffffffffffffffffffffffffffffffffffffffff
                )
            }
        } else {
            sender = msg.sender;
        }
        return sender;
    }

    function _execute(
        address to,
        bytes memory data,
        uint256 gasLimit,
        address sender
    ) internal returns (bool success) {
        bytes memory full = abi.encodePacked(data, sender);
        assembly {
            success := call(gasLimit, to, 0, add(full, 0x20), mload(full), 0, 0)
        }
    }