code: function(plugin) {
              var ns = plugin, 
                  plugins = this._plugins;
      
              if (L.isFunction(plugin)) {
                  ns = plugin.NS;
                  if (ns && (!plugins[ns] || plugins[ns] !== plugin)) {
                      ns = null;
                  }
              }
      
              if (ns) {
                  if (this[ns]) {
                      this[ns].destroy();
                      delete this[ns];
                  }
                  if (plugins[ns]) {
                      delete plugins[ns];
                  }
              }
          }
docs: Unplugs and destroys a plugin already instantiated with the host.
  
  @method _unplug
  @private
  @param {String | Function} plugin The namespace for the plugin, or a plugin class with the static NS property defined.