code: def remove_coreference_layer(self):
          
          if self.coreference_layer is not None:
              this_node = self.coreference_layer.get_node()
              self.root.remove(this_node)
          if self.header is not None:
              self.header.remove_lp('coreferences')
docs: Removes the constituency layer (if exists) of the object (in memory)