code: def last_idx(self) -> int:
      return self.tree.last_key()
  
imports: import numpy
  from typing import Any, Iterator, List, Tuple, Union
  from aim.storage.treeview import TreeView
  from aim.storage.arrayview import ArrayView
label_desc: Use image node_id 23 for calling the TreeArrayView obj's underlying member method code with example usage: obj.last_idx() and returns: self