How to use the klayout.QtCore function in klayout

def test_2(self):
    # Some smoke test
    v = QtCore.Qt.QT_VERSION
    self.assertEqual(v > 1, True)
    b = QtCore.QBuffer()
    b.setData("all you can eat")
    b.open(QtCore.QIODevice.ReadOnly)
    self.assertEqual(b.read(3), "all")
    b.read(1)
    self.assertEqual(b.read(3), "you")

def test_1(self):
    self.assertEqual("QBuffer" in QtCore.__all__, True)

def test_2(self):
    # Some smoke test
    b = QtCore.QBuffer()
    b.setData("abc")
    b.open(QtCore.QIODevice.ReadOnly)
    doc = QtXml.QDomDocument()
    doc.setContent(b)
    b.close()
    self.assertEqual(doc.documentElement().tagName, "doc")
    self.assertEqual(doc.documentElement().firstChild().toElement().tagName, "e")