code: async def bitcount(self, key, start=None, end=None):
          
          params = [key]
          if start is not None and end is not None:
              params.append(start)
              params.append(end)
          elif (start is not None and end is None) or \
                  (end is not None and start is None):
              raise RedisError("Both start and end must be specified")
          return await self.execute_command('BITCOUNT', *params)
docs: Returns the count of set bits in the value of ``key``.  Optional
          ``start`` and ``end`` paramaters indicate which bytes to consider