code: def install_required(self, type=None, service=None, list_only=0, **kwargs): # pylint: disable=redefined-builtin
          
          r = self.local_renderer
          list_only = int(list_only)
          type = (type or '').lower().strip()
          assert not type or type in PACKAGE_TYPES, 'Unknown package type: %s' % (type,)
          lst = []
          if type:
              types = [type]
          else:
              types = PACKAGE_TYPES
          for _type in types:
              if _type == SYSTEM:
                  content = '\n'.join(self.list_required(type=_type, service=service))
                  if list_only:
                      lst.extend(_ for _ in content.split('\n') if _.strip())
                      if self.verbose:
                          print('content:', content)
                      break
                  fd, fn = tempfile.mkstemp()
                  fout = open(fn, 'w')
                  fout.write(content)
                  fout.close()
                  self.install_custom(fn=fn)
              else:
                  raise NotImplementedError
          return lst
docs: Installs system packages listed as required by services this host uses.