Update plugin margins

def update_margins(self):
        """Update plugin margins"""
        layout = self.layout()
        if self.default_margins is None:
            self.default_margins = layout.getContentsMargins()
        if CONF.get('main', 'use_custom_margin'):
            margin = CONF.get('main', 'custom_margin')
            layout.setContentsMargins(*[margin]*4)
        else:
            layout.setContentsMargins(*self.default_margins)