code: function (cmd, callback) {
      var cmdName = dotty.get(cmd, this.definitions.command.name);
  
      var err;
      if (!cmdName) {
        err = new Error('command has no command name in ' + this.definitions.command.name);
        debug(err);
        return callback(err);
      }
  
      var version = 0;
      if (!!this.definitions.command.version) {
        version = dotty.get(cmd, this.definitions.command.version);
      }
  
      var command = this.getCommand(cmdName, version);
      if (!command) {
        err = new Error('Command "' + cmdName + '" not found!');
        debug(err);
        return callback(err);
      }
  
      if (command.validate.length >= 2) {
        return command.validate(cmd, callback);
      }
  
      try {
        callback(command.validate(cmd));
      } catch (e) {
        callback(e);
      }
    }
docs: Validates the requested command.
  @param {Object} cmd The command object
  @returns {ValidationError}