Removes the markable layer (if exists) of the object (in memory)

def remove_markable_layer(self):
        """
            Removes the markable layer (if exists) of the object (in memory)
            """
        if self.markable_layer is not None:
            this_node = self.markable_layer.get_node()
            self.root.remove(this_node)
        if self.header is not None:
            self.header.remove_lp('markables')