def __init__(self, assets_dir=None, requirements_file="requirements.yml"):
        self.assets_dir = assets_dir or Path(".") / "assets"
        self.requirements = GroupedRequirements()
        self.requirements.load(requirements_file)
        self.temp_dir = mkdtemp()
def _on_item_widget_size_allocate(self, item_widget, allocation, item):
    if item in self._items_allocations:
      self._update_width(allocation.width - self._items_allocations[item].width)
      self._update_height(allocation.height - self._items_allocations[item].height)
    else:
      self._update_width(allocation.width)
      self._update_height(allocation.height + self._item_spacing)