code: public static RaftAgent fromConfigurationFile(String configFile, RaftListener raftListener) throws IOException {
          RaftConfiguration configuration = RaftConfigurationLoader.loadFromFile(configFile);
          return fromConfigurationObject(configuration, raftListener);
      }
docs: Create an instance of {@code RaftAgent} from a configuration file.
  
  @param configFile location of the JSON configuration file. The
  configuration in this file will be validated.
  See the project README.md for more on the configuration file
  @param raftListener instance of {@code RaftListener} that will be notified of events from the Raft cluster
  @return valid {@code RaftAgent} that can be used to connect to, and (if leader),
  replicate {@link Command} instances to the Raft cluster
  @throws IOException if the configuration file cannot be loaded or processed (i.e. contains invalid JSON)