private void checkLearnersOpParams(final String groupId, final Configuration conf, final List<PeerId> learners) {
        Requires.requireTrue(!StringUtils.isBlank(groupId), "Blank group id");
        Requires.requireNonNull(conf, "Null configuration");
        Requires.requireTrue(learners != null && !learners.isEmpty(), "Empty peers");
        checkPeers(learners);
    }
Cli service implementation.

@author boyan (boyan@alibaba-inc.com)
@author jiachun.fjc
jraft-core/src/main/java/com/alipay/sofa/jraft/core/CliServiceImpl.java