class_docstr: A rolling univariate statistic measures a property of a variable over a window.
code: def window_size(self):
      pass
  
imports: from __future__ import annotations
  import abc
  import numbers
  from river import base
label_desc: Use image node_id 1 for calling the RollingUnivariate obj's underlying member method code with example usage: obj.window_size() without return types