Qwidget import with uic

I want to create a gui for a simple qgis-program (QGIS 2.18, Python 2.7). I have to import the gui-object with uic, as pyuic4 for some obscure reason won't work on my system (Ubuntu 18.04).

mask = uic.loadUi("abc") # import abc.ui mask

As a beginner, it is hard for me to track all the elements of the Widget-object. Is there a way to display the object properties?

I tried:

import inspect
inspect.getsource(mask)

But I got:

PyQt4.QtGui.QWidget object> is not a module, class, method, function, traceback, frame, or code object