class_docstr: Micro-cluster class.
code: def center(self):
      return {k: var.mean.get() for k, var in self.var_x.items()}
  
imports: from __future__ import annotations
  import math
  from collections import defaultdict
  from river import base, cluster, stats, utils
label_desc: Use image node_id 2 for calling the CluStreamMicroCluster obj's underlying member method code with example usage: obj.center() and returns: unknown