code: def follow_char(self, label, index):
          "Follows a transition"
          offset = units.offset(self._units[index])
          next_index = (index ^ offset ^ label) & units.PRECISION_MASK
  
          if units.label(self._units[next_index]) != label:
              return None
  
          return next_indef follow_char(self, label, index):
          "Follows a transition"
          offset = units.offset(self._units[index])
          next_index = (index ^ offset ^ label) & units.PRECISION_MASK
  
          if units.label(self._units[next_index]) != label:
              return None
  
          return next_index
docs: Follows a transition