code: def list_lib(self, repo):
          
          packages = ""
          if repo == "sbo":
              if (os.path.isfile(
                      self.meta.lib_path + "{0}_repo/SLACKBUILDS.TXT".format(
                          repo))):
                  packages = Utils().read_file(self.meta.lib_path + "{0}_repo/"
                                               "SLACKBUILDS.TXT".format(repo))
          else:
              if (os.path.isfile(
                      self.meta.lib_path + "{0}_repo/PACKAGES.TXT".format(repo))):
                  packages = Utils().read_file(self.meta.lib_path + "{0}_repo/"
                                               "PACKAGES.TXT".format(repo))
          return packages
docs: Return package lists