function set_required_validators_num(
    uint256 _required_validators
) external onlyRole(MANAGER_ROLE) {
    uint256 old = required_validators;
    required_validators = _required_validators;
    emit RequiredValidatorsChanged(msg.sender, old, required_validators);
}
it('PoC set_required_validators_num', async () => {
    const { settlmentInstance, verifierInstance, manager } = await loadFixture(deploySettlementFixture)
    await settlmentInstance.connect(manager).set_required_validators_num(3);

    expect(await settlmentInstance.required_validators()).to.equal(3);
    expect(await verifierInstance.required_validators()).to.equal(2); // does not changed
});
function set_required_validators_num(
    uint256 _required_validators
) external onlyRole(MANAGER_ROLE) {
+   signature_verifier.set_required_validators_num(_required_validators);
    uint256 old = required_validators;
    required_validators = _required_validators;
    emit RequiredValidatorsChanged(msg.sender, old, required_validators);
}
