def append(self, value, key=''):
        key = str(key)
        if not isinstance(value, Widget):
            raise ValueError('value should be a Widget (otherwise use add_child(key,other)')

        if 'left' in value.style.keys():
            del value.style['left']
        if 'right' in value.style.keys():
            del value.style['right']

        value.style['position'] = 'static'

        value.style['-webkit-order'] = '-1'
        value.style['order'] = '-1'

        # weight of the widget in the layout
        # value.style['-webkit-flex'] =
        # value.style['-ms-flex'] =
        # value.style['flex'] =

        key = str(id(value)) if key == '' else key
        self.add_child(key, value)

        if self.layout_orientation == Widget.LAYOUT_HORIZONTAL:
            if 'float' in self.children[key].style.keys():
                if not (self.children[key].style['float'] == 'none'):
                    self.children[key].style['float'] = 'left'
            else:
                self.children[key].style['float'] = 'left'

        return key
It allows to add child widgets to this.
dataset/ETHPy150Open dddomodossola/remi/remi/gui.py/HBox.append