docs: function knFetchAll(args, callback)
  {
  	var sources;
  
  	sources = args['sources'];
  	knValidateSources(sources);
  
  	knFetchSnapshots(sources, args['clientOptions'] || {},
  	    function (err, snapshots) {
  		if (snapshots)
  			snapshots = knMergeSnapshots(snapshots);
  		callback(err, snapshots);
  	    });
  }