ReferenceLineSet.sort() fails

from pfs.drp.stella import ReferenceLine, ReferenceLineSet
lines=[]
lines.append(ReferenceLine('OH', 3456.0, 1.234, 0))
lines.append(ReferenceLine('NaI', 1234.0, 3.0, 0))
lineSet = ReferenceLineSet.fromRows(lines)
lineSet.sort()

---------------------------------------------------------------------------
KeyError                                  Traceback (most recent call last)
<ipython-input-80-beabf8b7f75f> in <module>
      4 lines.append(ReferenceLine('NaI', 1234.0, 3.0, 0))
      5 lineSet = ReferenceLineSet.fromRows(lines)
----> 6 lineSet.sort()

/tigress/hassans/software/drp_stella/python/pfs/drp/stella/referenceLine.py in sort(self)
    159         Lines are sorted by species and then by wavelength.
    160         """
--> 161         self.data.sort_values(("description", "wavelength", "status"), inplace=True)
    162 
    163     def writeLineList(self, filename):

/tigress/HSC/PFS/stack/20190925/python/miniconda3-4.5.12/envs/lsst-scipipe/lib/python3.7/site-packages/pandas/core/frame.py in sort_values(self, by, axis, ascending, inplace, kind, na_position)
   4717 
   4718             by = by[0]
-> 4719             k = self._get_label_or_level_values(by, axis=axis)
   4720 
   4721             if isinstance(ascending, (tuple, list)):

/tigress/HSC/PFS/stack/20190925/python/miniconda3-4.5.12/envs/lsst-scipipe/lib/python3.7/site-packages/pandas/core/generic.py in _get_label_or_level_values(self, key, axis)
   1704             values = self.axes[axis].get_level_values(key)._values
   1705         else:
-> 1706             raise KeyError(key)
   1707 
   1708         # Check for duplicates

KeyError: ('description', 'wavelength', 'status')