class_docstr: Queue with Binary Indexed Tree cache
  
  queue-like data structure
  append, update are O(log n)
  reduction over an interval is O(log n) per query
class_docstr_tok: ["Queue","with","Binary","Indexed","Tree","cache","queue-like","data","structure","append",",","update","are","O","(","log","n",")","reduction","over","an","interval","is","O","(","log","n",")","per","query"]
code: def __setitem__(self, ix: int, val: V) -> None:
      assert 0 <= ix < self.length
      assert val is not None
      self._write(ix, val)
  
imports: import collections
  from typing import Any, Callable, Deque, Generic, List, Optional, Sequence, Tuple, TypeVar
  import numpy
  from pfrl.utils.random import sample_n_k
label_desc: Use image node_id 2 for calling the TreeQueue obj's underlying member method code with example usage: obj.__setitem__(ix, val) without return types