code: async def load_varint(reader):
      
      buffer = _UINT_BUFFER
  
      await reader.areadinto(buffer)
      width = int_mark_to_size(buffer[0] & PortableRawSizeMark.MASK)
      result = buffer[0]
  
      shift = 8
      for _ in range(width-1):
          await reader.areadinto(buffer)
          result += buffer[0] << shift
          shift += 8
      return result >> 2
docs: Binary load of variable size integer serialized by dump_varint
  
      :param reader:
      :return: