docstr: A proxy-call to the dataframe's `.mean()`.
code: def mean(self):
      """
      A proxy-call to the dataframe's `.mean()`.
      """
      return self.dataframe.mean()
  
imports: from abc import ABC
label_desc: Use image node_id 28 for calling the DataframeAbstract obj's underlying member method code with example usage: obj.mean() and returns: self