docs: function knFetchSchema(args, callback)
  {
  	var sources = args['sources'];
  	knValidateSources(sources);
  	knFetchMany(sources, {}, knFetchSchemaOne, function (err, schemas) {
  		if (err)
  			callback(err);
  		else
  			callback(null, knMergeSchemas(schemas));
  	});
  }