code: def subset(self, subset_pattern):
                  
          if subset_pattern is None:
              self._subset = None
          else:
              subset_pattern = subset_pattern.replace(',',':')
              self._subset = subset_pattern.replace(";",":").split(":")
docs: Limits inventory results to a subset of inventory that matches a given
          pattern, such as to select a given geographic of numeric slice amongst
          a previous 'hosts' selection that only select roles, or vice versa.  
          Corresponds to --limit parameter to ansible-playbook