def only_active_assets(reference_date_value, assets):
 return [a for a in assets if was_active(reference_date_value, a)]

def only_active_assets ( reference_date_value , assets ) : return [ a for a in assets if was_active ( reference_date_value , a ) ]
filter an iterable of asset objects down to just assets that were alive at the time corresponding to reference_date_value .