docs: def init_argparser(self, argparser):
          """
          Other runtimes (or users of ArgumentParser) can pass their
          subparser into here to collect the arguments here for a
          subcommand.
          """
  
          super(SourcePackageToolchainRuntime, self).init_argparser(argparser)
  
          self.init_argparser_source_registry(argparser)
          self.init_argparser_package_names(argparser)