code: def after_stat(x):
      """
      Evaluate mapping after statistic has been calculated
  
      Parameters
      ----------
      x : str
          An expression
  
      See Also
      --------
      plotnine.mapping.after_scale
      plotnine.mapping.stage
      """
      return stage(after_stat=x)
  
file_path: plotnine/plotnine/mapping/evaluation.py
imports: from __future__ import annotations
  import numbers
  import typing
  import numpy
  import pandas
  import pandas.api.types
  from ..exceptions import PlotnineError
label_desc: Use image node_id 1 for calling a global function with example usage: after_stat(x) and returns: stage