Returns
        -------
        list of tuples
            A list of the clicked (x, y) coordinates.

        Notes
        -----
        The keyboard can also be used to select points in case your mouse
        does not have one or more of the buttons.  The delete and backspace
        keys act like right-clicking (i.e., remove last point), the enter key
        terminates input and any other key (not already used by the window
        manager) selects a point.
        c