contract Pausable is Context {
  /**
    * @dev Emitted when the pause is triggered by `account`.
    */
  event Paused(address account);

  /**
    * @dev Emitted when the pause is lifted by `account`.
    */
  event Unpaused(address account);

  bool private _paused;

  /**
    * @dev Initializes the contract in unpaused state.
    */
  constructor () internal {
    _paused = false;
  }

  /**
    * @dev Returns true if the contract is paused, and false otherwise.
    */
  function paused() public view returns (bool) {
    return _paused;
  }

  /**
    * @dev Modifier to make a function callable only when the contract is not paused.
    *
    * Requirements:
    *
    * - The contract must not be paused.
    */
  modifier whenNotPaused() {
    require(!_paused, "Pausable: paused");
    _;
  }

  /**
    * @dev Modifier to make a function callable only when the contract is paused.
    *
    * Requirements:
    *
    * - The contract must be paused.
    */
  modifier whenPaused() {
    require(_paused, "Pausable: not paused");
    _;
  }

  /**
    * @dev Triggers stopped state.
    *
    * Requirements:
    *
    * - The contract must not be paused.
    */
  function _pause() internal virtual whenNotPaused {
    _paused = true;
    emit Paused(_msgSender());
  }

  /**
    * @dev Returns to normal state.
    *
    * Requirements:
    *
    * - The contract must be paused.
    */
  function _unpause() internal virtual whenPaused {
    _paused = false;
    emit Unpaused(_msgSender());
  }
}
/**
 * @dev Contract module which allows children to implement an emergency stop
 * mechanism that can be triggered by an authorized account.
 *
 * This module is used through inheritance. It will make available the
 * modifiers `whenNotPaused` and `whenPaused`, which can be applied to
 * the functions of your contract. Note that they will not be pausable by
 * simply including this module, only once the modifiers are put in place.
 */
function _pause() internal virtual whenNotPaused {
    _paused = true;
    emit Paused(_msgSender());
  }
/**
 * @dev Triggers stopped state.
 *
 * Requirements:
 *
 * - The contract must not be paused.
 */