<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def action_aggregate(reader, *args):
 """Aggregate flow records by 5-tuple and print a tab-separated stream"""

    all_aggregated = aggregated_records(reader)
    first_row = next(all_aggregated)
    keys = sorted(first_row.keys())
    print(*keys, sep='\t')

    # Join the first row with the rest of the rows and print them
    iterable = chain([first_row], all_aggregated)
    for item in iterable:
        print(*[item[k] for k in keys], sep='\t')