The SourceList represents the sources rubygems has been configured to use. A source may be created from an array of sources:
Gem::SourceList.from %w[https://rubygems.example https://internal.example]
Or by adding them:
sources = Gem::SourceList.new sources << 'https://rubygems.example'
The most common way to get a SourceList is Gem.sources
.