code: def add(self, x: int, weight: int = 1) -> None:
      if weight == 0:
          return
      n1 = self._weight
      n2 = weight
      n = n1 + n2
      M = (n1 * self._mean + n2 * x) / n
      self._weight = n
      self._mean = M
  
file_path: ray/python/ray/data/_internal/size_estimator.py
imports: from typing import Any, List
  import ray
  from ray import cloudpickle
label_desc: Use image node_id 2 for calling the RunningMean obj's underlying member method code with example usage: obj.add(x, weight) without return types