code: def update(self):
          
          packager = self.packager
          if packager == APT:
              self.sudo('DEBIAN_FRONTEND=noninteractive apt-get -yq update')
          elif packager == YUM:
              self.sudo('yum update')
          else:
              raise Exception('Unknown packager: %s' % (packager,))
docs: Preparse the packaging system for installations.