code: def load(cls, primary_key, convert_key=True):
          
          if convert_key:
              primary_key = cls._query.get_primary_hash_key(primary_key)
          if not cls.__database__.hash_exists(primary_key):
              raise KeyError('Object not found.')
          raw_data = cls.__database__.hgetall(primary_key)
          if PY3:
              raw_data = decode_dict_keys(raw_data)
          data = {}
          for name, field in cls._fields.items():
              if isinstance(field, _ContainerField):
                  continue
              elif name in raw_data:
                  data[name] = field.python_value(raw_data[name])
              else:
                  data[name] = None
  
          return cls(**data)
docs: Retrieve a model instance by primary key.
  
          :param primary_key: The primary key of the model instance.
          :returns: Corresponding :py:class:`Model` instance.
          :raises: ``KeyError`` if object with given primary key does
              not exist.