code: function (specification, opts, callback) {
      var executeSync = load('sync');
  
      if (arguments.length > 0) {
        if (typeof specification === 'string') {
          this.internals.argv.destination = specification;
        }
  
        if (typeof opts === 'string') {
          this.internals.migrationMode = opts;
          this.internals.matching = opts;
        } else if (typeof opts === 'function') {
          callback = opts;
        }
      }
  
      return Promise.fromCallback(
        function (callback) {
          executeSync(this.internals, this.config, callback);
        }.bind(this)
      ).asCallback(callback);
    }
docs: Executes up a given number of migrations or a specific one.
  
  Defaults to up all migrations if no count is given.