def densely_packed_versions
      if @densely_packed_versions.nil?
        @densely_packed_versions = DenselyPackedSet.new(versions.map{|pkg_version| pkg_version.version})
        Debug.log.debug { "Package Versions for '#{@name}' :" }
        versions.each do |v|
          Debug.log.debug { "    #{v.to_s(true)}" }
        end
      end
      @densely_packed_versions
    end
def densely_packed_versions
      if @densely_packed_versions.nil?
        @densely_packed_versions = DenselyPackedSet.new(versions.map{|pkg_version| pkg_version.version})
        Debug.log.debug { "Package Versions for '#{@name}' :" }
        versions.each do |v|
          Debug.log.debug { "    #{v.to_s(true)}" }
        end
      end
      @densely_packed_versions
    end
Note: only invoke this method after all PackageVersions have been added