class_docstr: Track a series of values and provide access to smoothed values over a
  window or the global series average.
code: def __init__(self, window_size=20):
      self.window_size = window_size
      self.reset()
  
imports: from collections import defaultdict, deque
  import torch
  from mmf.common.registry import registry
  from mmf.utils.distributed import reduce_dict
  from mmf.utils.general import scalarize_dict_values
label_desc: Use image node_id 1 to create a new SmoothedValue object  with example: obj = SmoothedValue(window_size)