code: function (namespaces) {
      _.forEach(namespaces, function (level, namespace) {
        cache.add(namespace, level);
      });
      return this;
    }
docs: set the namespaces configuration.
  
  Config object
  ```
  {
  'root': 'all',
  'namespace1.namespace2': 'info',
  }
  ```
  
  **root** namespace is for all unknown namespaces.
  
  @param {object} namespaces the map with the namespace and its log level
  @return {self}