# File lib/dep_selector/package.rb, line 48
    def [](version_or_constraint)
      # version constraints must abide the include? contract
      if version_or_constraint.respond_to?(:include?)
        versions.select do |ver|
          version_or_constraint.include?(ver)
        end
      else
        versions.find{|pkg_version| pkg_version.version == version_or_constraint}
      end
    end