Generate a reference to each layout placeholder on this slide layout
        that should be cloned to a slide when the layout is applied to that
        slide.

def iter_cloneable_placeholders(self):
        """
        Generate a reference to each layout placeholder on this slide layout
        that should be cloned to a slide when the layout is applied to that
        slide.
        """
        latent_ph_types = (
            PP_PLACEHOLDER.DATE, PP_PLACEHOLDER.FOOTER,
            PP_PLACEHOLDER.SLIDE_NUMBER
        )
        for ph in self.placeholders:
            if ph.element.ph_type not in latent_ph_types:
                yield ph