contract Controllable {

    address public controller;

    modifier onlyController() {
        require(msg.sender == controller, "Can only be called by controller");
        _;
    }

    /// @notice Changes the controller who is allowed to deprecate or remove limits.
    /// Can only be called by the controller.
    function changeController(address new_controller)
        external
        onlyController
    {
        controller = new_controller;
    }
}
// MIT License
// Copyright (c) 2018
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
// The above copyright notice and this permission notice shall be included in all
// copies or substantial portions of the Software.
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
// SOFTWARE.
function changeController(address new_controller)
    external
    onlyController
{
    controller = new_controller;
}

/// @notice Changes the controller who is allowed to deprecate or remove limits.
/// Can only be called by the controller.