docs: def start(self, is_upgrade):
          """
          Install packages from official Slackware distribution
          """
          self.case_insensitive()
          # fix if packages is for upgrade
          self.is_upgrade = is_upgrade
          mas_sum = dep_sum = sums = [0, 0, 0]
          self.msg.done()
          self.dependencies = self.resolving_deps()
          self.update_deps()
          (self.dep_dwn, self.dep_install, self.dep_comp_sum,
              self.dep_uncomp_sum) = self.store(self.dependencies)
          self.clear_masters()
          (self.dwn, self.install, self.comp_sum,
              self.uncomp_sum) = self.store(self.packages)
          if (self.meta.rsl_deps in ["on", "ON"] and
                  "--resolve-off" not in self.flag):
              self.msg.done()
          if self.install:
              if self.matching and [""] != self.packages:
                  self.msg.matching(self.packages)
              else:
                  print("\nThe following packages will be automatically "
                        "installed or upgraded \nwith new version:\n")
              self.top_view()
              self.msg.upg_inst(self.is_upgrade)
              mas_sum = self.views(self.install, self.comp_sum)
              if self.dependencies:
                  print("Installing for dependencies:")
                  dep_sum = self.views(self.dep_install, self.dep_comp_sum)
              # sums[0] --> installed
              # sums[1] --> upgraded
              # sums[2] --> uninstall
              sums = [sum(i) for i in zip(mas_sum, dep_sum)]
              unit, size = units(self.comp_sum + self.dep_comp_sum,
                                 self.uncomp_sum + self.dep_uncomp_sum)
              if self.matching and [""] != self.packages:
                  print("\nMatching summary")
                  print("=" * 79)
                  print("Total {0} matching packages\n".format(sum(sums)))
                  raise SystemExit(1)
              print("\nInstalling summary")
              print("=" * 79)
              print("{0}Total {1} {2}.".format(self.meta.color["GREY"],
                                               sum(sums),
                                               self.msg.pkg(sum(sums))))
              print("{0} {1} will be installed, {2} will be upgraded and "
                    "{3} will be reinstalled.".format(sums[2],
                                                      self.msg.pkg(sums[2]),
                                                      sums[1], sums[0]))
              print("Need to get {0} {1} of archives.".format(size[0],
                                                              unit[0]))
              print("After this process, {0} {1} of additional disk "
                    "space will be used.{2}".format(size[1], unit[1],
                                                    self.meta.color["ENDC"]))
              print("")
              self.if_all_installed()
              if self.msg.answer() in ["y", "Y"]:
                  for inst, dwn in zip(self.dep_install + self.install,
                                       self.dep_dwn + self.dwn):
                      if (self.meta.not_downgrade == "on" and
                              self.not_downgrade(inst) is True):
                          continue
                      if (not os.path.isfile(self.meta.pkg_path + inst[:-4]) or
                              "--download-only" in self.flag or
                              "--reinstall" in self.flag):
                          Download(self.tmp_path, dwn.split(), self.repo).start()
                      else:
                          self.msg.template(78)
                          self.msg.pkg_found(inst)
                          self.msg.template(78)
                  if "--download-only" in self.flag:
                      raise SystemExit()
                  self.dep_install = Utils().check_downloaded(
                      self.tmp_path, self.dep_install)
                  self.install = Utils().check_downloaded(
                      self.tmp_path, self.install)
                  ins, upg = self.install_packages()
                  self.msg.reference(ins, upg)
                  write_deps(self.deps_dict)
                  delete_package(self.tmp_path, self.dep_install + self.install)
          else:
              self.msg.not_found(self.is_upgrade)
              raise SystemExit(1)