How to use the pyperclip._executable_exists function in pyperclip

import PyQt4
            except ImportError:
                pass
            else:
                clipboard = init_qt_clipboard()
        else:
            clipboard = init_qt_clipboard()


class TestXClip(_TestClipboard):
    if _executable_exists("xclip"):
        clipboard = init_xclip_clipboard()


class TestXSel(_TestClipboard):
    if _executable_exists("xsel"):
        clipboard = init_xsel_clipboard()


class TestKlipper(_TestClipboard):
    if _executable_exists("klipper") and _executable_exists("qdbus"):
        clipboard = init_klipper_clipboard()


class TestNoClipboard(unittest.TestCase):
    copy, paste = init_no_clipboard()

    def test_copy(self):
        with self.assertRaises(RuntimeError):
            self.copy("foo")

    def test_paste(self):

else:
            clipboard = init_qt_clipboard()


class TestXClip(_TestClipboard):
    if _executable_exists("xclip"):
        clipboard = init_xclip_clipboard()


class TestXSel(_TestClipboard):
    if _executable_exists("xsel"):
        clipboard = init_xsel_clipboard()


class TestKlipper(_TestClipboard):
    if _executable_exists("klipper") and _executable_exists("qdbus"):
        clipboard = init_klipper_clipboard()


class TestNoClipboard(unittest.TestCase):
    copy, paste = init_no_clipboard()

    def test_copy(self):
        with self.assertRaises(RuntimeError):
            self.copy("foo")

    def test_paste(self):
        with self.assertRaises(RuntimeError):
            self.paste()


if __name__ == '__main__':

if HAS_DISPLAY:
        try:
            import PyQt5
        except ImportError:
            try:
                import PyQt4
            except ImportError:
                pass
            else:
                clipboard = init_qt_clipboard()
        else:
            clipboard = init_qt_clipboard()


class TestXClip(_TestClipboard):
    if _executable_exists("xclip"):
        clipboard = init_xclip_clipboard()


class TestXSel(_TestClipboard):
    if _executable_exists("xsel"):
        clipboard = init_xsel_clipboard()


class TestKlipper(_TestClipboard):
    if _executable_exists("klipper") and _executable_exists("qdbus"):
        clipboard = init_klipper_clipboard()


class TestNoClipboard(unittest.TestCase):
    copy, paste = init_no_clipboard()