library Roles
{
  struct Role
  {
    mapping(address => bool) bearer;
  }

  /**
   * @dev Give an account access to this role.
   */
  function add(Role storage role, address account) internal
  {
    require(!has(role, account), "has role");
    role.bearer[account] = true;
  }

  /**
   * @dev Remove an account's access to this role.
   */
  function remove(Role storage role, address account) internal
  {
    require(has(role, account), "!has role");
    role.bearer[account] = false;
  }

  /**
   * @dev Check if an account has this role.
   * @return bool
   */
  function has(Role storage role, address account) internal view returns (bool)
  {
    require(account != address(0), "Roles: 0 addy");

    return role.bearer[account];
  }
}
/**
 * @title Roles
 * @dev Library for managing addresses assigned to a Role.
 */
function remove(Role storage role, address account) internal
{
  require(has(role, account), "!has role");
  role.bearer[account] = false;
}

/**
 * @dev Remove an account's access to this role.
 */