How to use the jake.Task function in jake

jake.exec(command, { printStdout: true, printStderr: true }, function() {
        jake.Task["check-coverage"].invoke();
        complete();
    });

var FILE = require("file"),
    OS = require("os"),
    UTIL = require("narwhal/util"),
    TERM = require("narwhal/term"),
    Jake = require("jake"),
    CLEAN = require("jake/clean").CLEAN,
    CLOBBER = require("jake/clean").CLOBBER,
    base64 = require("base64"),
    ObjectiveJ = require("objective-j"),
    environment = require("objective-j/jake/environment"),
    task = Jake.task;

var Task = Jake.Task,
    filedir = Jake.filedir;

function isImage(/*String*/ aFilename)
{
    return UTIL.has([".png", ".jpg", ".jpeg", ".gif", ".tif", ".tiff"], FILE.extension(aFilename).toLowerCase());
}

function mimeType(/*String*/ aFilename)
{
    return  {
                ".png"  : "image/png",
                ".jpg"  : "image/jpeg",
                ".jpeg" : "image/jpeg",
                ".gif"  : "image/gif",
                ".tif"  : "image/tiff",
                ".tiff" : "image/tiff"