shops.plot() draws one line per column, with the row labels along the bottom. But the café chain's data comes as a long list: one record per shop per day, and sometimes a shop sends two records for the same day.
Task: write lines_per_shop(days, shops, visitors, day_order). Record i says shop shops[i] had visitors[i] visitors on day days[i].
Return a dictionary with one key per shop. Each value is that shop's line: a list of its total visitors on each day, in the order of day_order.
0.day_order has at least one record, and every record's day is in day_order.