    def __init__(self, screen, renderer, y, colour, bg=Screen.COLOUR_BLACK, **kwargs):
        """
        :param screen: The Screen being used for the Scene.
        :param renderer: The renderer to be scrolled
        :param y: The line (y coordinate) for the start of the text.
        :param colour: The default foreground colour to use for the text.
        :param bg: The default background colour to use for the text.

        Also see the common keyword arguments in :py:obj:`.Effect`.
        """
        super().__init__(screen, **kwargs)
        self._renderer = renderer
        self._y = y
        self._colour = colour
        self._bg = bg
        self._text_pos = None
        self._scr_pos = None
:param screen: The Screen being used for the Scene.
:param renderer: The renderer to be scrolled
:param y: The line (y coordinate) for the start of the text.
:param colour: The default foreground colour to use for the text.
:param bg: The default background colour to use for the text.

Also see the common keyword arguments in :py:obj:`.Effect`.
asciimatics/effects.py