temperature error

Traceback (most recent call last):
    print(obj["temperature"])
    self.get_data(f)
  File "/opt/apps/yt/yt-x86_64/src/yt-hg/yt/data_objects/construction_data_containers.py", line 602, in get_data
    if len(fill) > 0: self._fill_fields(fill)
  File "/opt/apps/yt/yt-x86_64/src/yt-hg/yt/data_objects/construction_data_containers.py", line 787, in _fill_fields
    raise NotImplementedError
NotImplementedError