function save(namespaces) {
		  if (null == namespaces) {
		    // If you set a process.env field to null or undefined, it gets cast to the
		    // string 'null' or 'undefined'. Just delete instead.
		    delete process.env.DEBUG;
		  } else {
		    process.env.DEBUG = namespaces;
		  }
		}
Get the priority of a media type.
@private