code: def add_placeholder(self, id_, name, ph_type, orient, sz, idx):
          
          sp = CT_Shape.new_placeholder_sp(
              id_, name, ph_type, orient, sz, idx
          )
          self.insert_element_before(sp, 'p:extLst')
          return sp
docs: Append a newly-created placeholder ``<p:sp>`` shape having the
          specified placeholder properties.