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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def initQApplication():
 """ Initializes the QtWidgets.QApplication instance. Creates one if it doesn't exist. Sets Argos specific attributes, such as the OrganizationName, so that the application persistent settings are read/written to the correct settings file/winreg. It is therefore important to call this function at startup. The ArgosApplication constructor does this. Returns the application. """

    # PyQtGraph recommends raster graphics system for OS-X.
    if 'darwin' in sys.platform:
        graphicsSystem = "raster" # raster, native or opengl
        os.environ.setdefault('QT_GRAPHICSSYSTEM', graphicsSystem)
        logger.info("Setting QT_GRAPHICSSYSTEM to: {}".format(graphicsSystem))

    app = QtWidgets.QApplication(sys.argv)
    initArgosApplicationSettings(app)
    return app