class_docstr: A simple counter.
  
  Attributes
  ----------
  n : int
      The current number of observations.
code: def update(self, x=None):
      self.n += 1
  
imports: from __future__ import annotations
  from river import stats
label_desc: Use image node_id 2 for calling the Count obj's underlying member method code with example usage: obj.update(x) without return types