code: def get_int_id(self, str_id):
          
          if not str_id in self.mapping:
              if self.curr_id == IdRemapper.INT_MAX:
                  return None # No more 32 bits signed integers available
              self.mapping[str_id] = self.curr_id
              self.r_mapping[self.curr_id] = str_id
              self.curr_id += 1
          return self.mapping[str_id]
docs: Get a unique 32 bits signed integer for the given string Id.