code: def update(self):
          
  
          self._copyfiles = False
          self._updatefiles = True
          self._purge = False
          self._creatdirs = False
  
          if self._verbose:
              self.log('Updating directory %s with %s\n' %
                       (self._dir2, self._dir1))
          self._dirdiffandupdate(self._dir1, self._dir2)
docs: Update will try to update the target directory
          w.r.t source directory. Only files that are common
          to both directories will be updated, no new files
          or directories are created