docs: def col_mod(df,col_name,func,*args,**kwargs):
      """ Changes a column of a DataFrame according to a given function
      Parameters:
      df - DataFrame
          DataFrame to operate on
      col_name - string
          Name of column to modify
      func - function
          The function to use to modify the column
      """
      backup = df[col_name].copy()
      try:
          return_val = func(df,col_name,*args,**kwargs)
          if return_val is not None:
              set_col(df,col_name,return_val)
      except:
          df[col_name] = backup