code: def variation(df: "DataFrame", ddof=1):
      return std(df, ddof=ddof) / mean(df)
  
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 9 for calling a global function with example usage: variation(df, ddof) and returns: unknown