Who is The Sirians from Shikasta: Re, Colonised Planet 5: Personal, Psychological, Historical... and what is their importance?

The Sirians are depicted as a kind of neutral-good third-party in Shikasta. Once enemies of the Canopeans, they have been friends and allied since the war. The Sirians set up experiments in Rohanda's southern hemisphere, but removed those experiments upon their completion. They did, however, keep agents on the planet, who sometimes aided the Canopeans in their struggle to save Shikasta from the Shammat.