code: def preprocess(df, stock_list):
      n = len(stock_list)
      N = df.shape[0]
      assert N % n == 0
      d = int(N / n)
      stock1_ary = df.iloc[0:d, 1:].values
      temp_ary = stock1_ary
      for j in range(1, n):
          stocki_ary = df.iloc[j * d : (j + 1) * d, 1:].values
          temp_ary = np.hstack((temp_ary, stocki_ary))
      return temp_ary
  
file_path: FinRL/finrl/meta/data_processors/processor_joinquant.py
imports: from __future__ import annotations
  import copy
  import os
  import jqdatasdk
  import numpy
  import pandas
  from func import calc_all_filenames
  from func import date2str
  from func import remove_all_files
label_desc: Use image node_id 4 for calling the JoinQuantEngineer obj's underlying member method code with example usage: obj.preprocess(df, stock_list) and returns: temp_ary