FIX: modified parse_cohorts() method to return generator
FIX: modified parse_cohorts() method to return generator

wikimedia/user_metrics,rfaulkner/wikipedia_user_metrics,rfaulkner/wikipedia_user_metrics,wikimedia/user_metrics,wikimedia/user_metrics,wikimedia/analytics-user-metrics,wikimedia/analytics-user-metrics,rfaulkner/wikipedia_user_metrics,wikimedia/analytics-user-metrics