Version 0.5.2 of the Sitecore Cloud SDK improves search capabilities with the new sources attribute, which lets you add a list of source IDs when you request content from Sitecore Search. If you do this, results will only be retrieved from the sources you listed, which is especially useful when filtering search results in a multi-site setup.
To get started, locate the IDs of the Sitecore Search sources you want to return results from, and add them to the source attribute for the relevant widget items, such as those used to request search results, recommendation content, or suggestions.