<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def import_dashboards(session, data_stream, import_time=None):
 """Imports dashboards from a stream to databases"""

    current_tt = int(time.time())
    import_time = current_tt if import_time is None else import_time
    data = json.loads(data_stream.read(), object_hook=decode_dashboards)
    # TODO: import DRUID datasources
    for table in data['datasources']:
        type(table).import_obj(table, import_time=import_time)
    session.commit()
    for dashboard in data['dashboards']:
        Dashboard.import_obj(
            dashboard, import_time=import_time)
    session.commit()