Support for the Ruby 2.4 series has ended. See here for reference.
The SourceSet chooses the best available method to query a remote index.
Kind off like BestSet but filters the sources for gems
Creates a SourceSet for the given sources or Gem::sources if none are specified. sources must be a Gem::SourceList.
# File rubygems/resolver/source_set.rb, line 12
def initialize
super()
@links = {}
@sets = {}
end