class_docstr: Class for incrementally computing the variance of a series of numbers.
class_docstr_tok: ["Class","for","incrementally","computing","the","variance","of","a","series","of","numbers","."]
code: def add(self, x):
      self.n += 1
      self.ex.add(x)
      self.ex2.add(x**2)
  
imports: from abc import abstractmethod
  from typing import List
  from math import sqrt
  import numpy
label_desc: Use image node_id 2 for calling the Variance obj's underlying member method code with example usage: obj.add(x) without return types