class_docstr: Handles/stores incoming dataset and provides window-based statistics.
  
  .. testcode::
      :skipif: True
  
      win_stats = WindowStat("level", 3)
      win_stats.push(5.0)
      win_stats.push(7.0)
      win_stats.push(7.0)
      win_stats.push(10.0)
      # Expect 8.0 as the mean of the last 3 values: (7+7+10)/3=8.0
      print(win_stats.mean())
  
  .. testoutput::
  
      8.0
docstr: Returns ndarray with 0, 10, 50, 90, and 100 percentiles.
docstr_tok: ["Returns","ndarray","with","0",",","10",",","50",",","90",",","and","100","percentiles","."]
code: def quantiles(self) -> np.ndarray:
      """Returns ndarray with 0, 10, 50, 90, and 100 percentiles."""
      if not self.count:
          return np.ndarray([], dtype=np.float32)
      else:
          return np.nanpercentile(
              self.items[: self.count], [0, 10, 50, 90, 100]
          ).tolist()
  
file_path: ray/rllib/utils/metrics/window_stat.py
imports: import numpy
label_desc: Use image node_id 5 for calling the WindowStat obj's underlying member method code with example usage: obj.quantiles() and returns: np, np