FarmerRole.sol

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;
...

function addFarmer(address account) public onlyFarmer {
        _addFarmer(account);
    }

    function renounceFarmer() public {
        _removeFarmer(_msgSender());
    }

    function _addFarmer(address account) internal {
        farmers.add(account);
        emit FarmerAdded(account);
    }

    function _removeFarmer(address account) internal {
        farmers.remove(account);
        emit FarmerRemoved(account);
    }
  ...