API:

p = foreman.get('/discovered_hosts')
for i in p['results']:

... print(i['id'])
562
533
513
432
362
361
289
287
284
283

p = foreman.get('/discovered_hosts?search=facts.is_virtual%3D+false')
for i in p['results']:

... print(i['id'])
562
533
432
432
362
361
289
287
287
284
284
283

pgsql:
foreman=> select id from hosts where type='Host::Discovered';
id
-------
432
562
289
287
284
283
361
533
362
513
(10 rows)