How to use the pympress.document.PdfPage function in pympress

if ar >= 2:
            try:
                return PdfPage[horizontal.upper()]
            except KeyError:
                return PdfPage.RIGHT

        # Make exception for classic american letter format and ISO (A4, B5, etc.)
        if abs(ar - 8.5 / 11) < 1e-3 or abs(ar - 1 / math.sqrt(2)) < 1e-3:
            return PdfPage.NONE

        # If the aspect ratio is < 1, we can assume it is a document with notes above or below.
        if ar < 1:
            try:
                return PdfPage[vertical.upper()]
            except KeyError:
                return PdfPage.BOTTOM

        return PdfPage.NONE

def scale(val):
        """ Return the enum value that does only scaling not shifting.
        """
        return PdfPage(val | 1)

# "Regular" slides will have an aspect ratio of 4/3, 16/9, 16/10... i.e. in the range [1..2]
        # So if the aspect ratio is >= 2, we can assume it is a document with notes on the side.
        if ar >= 2:
            try:
                return PdfPage[horizontal.upper()]
            except KeyError:
                return PdfPage.RIGHT

        # Make exception for classic american letter format and ISO (A4, B5, etc.)
        if abs(ar - 8.5 / 11) < 1e-3 or abs(ar - 1 / math.sqrt(2)) < 1e-3:
            return PdfPage.NONE

        # If the aspect ratio is < 1, we can assume it is a document with notes above or below.
        if ar < 1:
            try:
                return PdfPage[vertical.upper()]
            except KeyError:
                return PdfPage.BOTTOM

        return PdfPage.NONE

def change_notes_pos(self, widget, event = None, force_change = False):
        """ Switch the position of the nodes in the slide.

        Returns:
            `bool`: whether the mode has been toggled.
        """
        if issubclass(type(widget), Gtk.CheckMenuItem):
            # if this widget is not the active one do nothing
            if not widget.get_active():
                return False
            target_mode = document.PdfPage[widget.get_name()[len('notes_'):].upper()]
        elif issubclass(type(widget), document.PdfPage):
            target_mode = widget
        else:
            return False

        # Redundant toggle, do nothing
        if target_mode == self.chosen_notes_mode:
            return False

        # Update the choice, except for NONE
        if target_mode:
            self.chosen_notes_mode = target_mode
            self.get_object('notes_' + target_mode.name.lower()).set_active(True)
            self.config.set('notes position', target_mode.direction(), target_mode.name.lower())

        # Change the notes arrangement if they are enabled or if we are forced to
        if self.notes_mode or force_change:

Pass 2 floats to transform coordinates, 4 to transform margins,
        i.e. the second pair of coordinates is taken from the opposite corner.

        Args:
            x1 (`float`): x coordinate on the page, on a scale 0..1
            y1 (`float`): y coordinate on the page, on a scale 0..1
            x2 (`float`): second x coordinate on the page, from the other side, on a scale 0..1
            y2 (`float`): second y coordinate on the page, from the other side, on a scale 0..1
        """
        if val == PdfPage.RIGHT:
            screen = (x * 2 - 1, y)
        elif val == PdfPage.LEFT:
            screen = (x * 2, y)
        elif val == PdfPage.BOTTOM:
            screen = (x, y * 2 - 1)
        elif val == PdfPage.TOP:
            screen = (x, y * 2)
        else:
            screen = (x, y)

        if x2 is None or y2 is None:
            return screen
        else:
            return screen + val.complement().to_screen(x2, y2)