code: function assetFingerprint(label, fingerprint, cacheInfo) {
  		if(arguments.length > 1)
  		{
  			//Add a label
  			var labelInfo = labels[label] = {"fingerprint": fingerprint};
  			if(cacheInfo)
  				for(var i in cacheInfo)
  					labelInfo[i] = cacheInfo[i];
  		}
  		else
  		{
  			//Try to get a fingerprint from a registered label
  			var info = labels[label];
  			if(info)
  			{
  				fingerprints[info.fingerprint] = info;
  				return info.fingerprint;
  			}
  			else
  			{
  				info = {};
  				//Try to get a fingerprint using the specified cache strategy
  				var fullPath = path.resolve(rootPath + "/" + (label || this.url) );
  				//Use the "cache strategy" to get a fingerprint
  				//Prefer the use of etag over lastModified when generating fingerprints
  				if(!fs.existsSync(fullPath) )
  					return label;
  				if(strategy.lastModified)
  				{
  					var mdate = info.lastModified = strategy.lastModified(fullPath);
  					mdate.setMilliseconds(0);
  				}
  				if(strategy.etag)
  					info.etag = strategy.etag(fullPath);
  				if(strategy.expires)
  					info.expires = strategy.expires(fullPath);
  				if(strategy.fileFingerprint)
  				{
  					var fingerprint = strategy.fileFingerprint(label, fullPath);
  					fingerprints[fingerprint] = info;
  					return fingerprint;
  				}
  				else
  					return label; //Do not generate a fingerprint
  			}
  		}
  	}
docs: req.assetFingerprint function