code: def _installer(self, package_list, install_string=None):
          
          packages = ' '.join(package_list)
  
          if install_string is None:
              self.install_string = self.install_process[self.distro] % packages
          else:
              self.install_string = install_string
  
          output, outcome = self.shell.run_command(command=self.install_string)
  
          if outcome is False:
              raise IOError(output)
docs: Install operating system packages for the system.
  
          :param: package_list: ``list``
          :param install_string: ``str``