class_docstr: Running sum.
  
  Attributes
  ----------
  sum : float
      The running sum.
  
  Examples
  --------
  
  >>> from river import stats
  
  >>> X = [-5, -3, -1, 1, 3, 5]
  >>> mean = stats.Sum()
  >>> for x in X:
  ...     mean.update(x)
  ...     print(mean.get())
  -5.0
  -8.0
  -9.0
  -8.0
  -5.0
  0.0
  
  >>> from river import utils
  
  >>> X = [1, -4, 3, -2, 2, 1]
  >>> rolling_sum = utils.Rolling(stats.Sum(), window_size=2)
  >>> for x in X:
  ...     rolling_sum.update(x)
  ...     print(rolling_sum.get())
  1.0
  -3.0
  -1.0
  1.0
  0.0
  3.0
code: def update(self, x):
      self.sum += x
  
file_path: river/river/stats/summing.py
imports: from __future__ import annotations
  from river import stats
label_desc: Use image node_id 2 for calling the Sum obj's underlying member method code with example usage: obj.update(x) without return types