new_contents: # importing modules/ libraries
  import pandas as pd
  import numpy as np
  
  orders_prior_df = pd.read_csv('Data/orders_prior_sample.csv')
  print('length of orders_prior_df:', len(orders_prior_df))
  
  order_products_prior_df = pd.read_csv('Data/order_products_prior_sample.csv')
  print('length of order_products_prior_df:', len(order_products_prior_df))
  
  grouped = order_products_prior_df.groupby('order_id')
  
  grouped_data = pd.DataFrame()
  
  grouped_data['order_id'] = grouped['order_id'].aggregate(np.mean)
  
  def product_ids(group):
      l = []
      ord_id = group['order_id']
      for e in group['product_id']:
          l.append(str(e))
      return ' '.join(l)
  
  grouped_data['product_ids'] = grouped.apply(product_ids)
  print('length of grouped_data:', len(grouped_data))
  
  orders_prior_merged = pd.merge(orders_prior_df, grouped_data, on='order_id')
  print('length of orders_prior_merged:', len(orders_prior_merged))
  
subject: Merge prior product ids with orders ids first pass