code: def mean(df: "DataFrame") -> "pd.Series":
      return sum(df) / df.shape[0]
  
file_path: FATE/python/fate/arch/dataframe/ops/_stat.py
imports: import functools
  import numpy
  import pandas
  import torch
  from .._dataframe import DataFrame
  from ..manager import DataManager
label_desc: Use image node_id 4 for calling a global function with example usage: mean(df) and returns: unknown