def METHOD_NAME(toolbox, specification=None, item=None, **kwargs):
    """
    Creates the item's specification widget.
    Subclasses that do not support specifications can still raise :class:`NotImplementedError`.
    Args:
        toolbox (ToolboxUI): Toolbox main window
        specification (ProjectItemSpecification, optional): a specification to show in the widget or None for
            a fresh start
        item (ProjectItem, optional): a project item. If the specification is accepted, it is also set for this item
        **kwargs: parameters passed to the specification widget
    Returns:
        QWidget: item's specification widget
    """
    raise NotImplementedError()