Cannot process simple Caliper sampling file

I created a Caliper sampling profile with
CALI_CONFIG=hatchet-sample-profile,source.function=true,source.location=true,source.module=true,sample.frequency=1000 ./a.out
using Caliper's cxx-example.cpp (see here).

The sampling output file is attached here: sample_profile.cali.txt
(I had to add .txt extension to be able to upload it.)

Next, I tried printing a tree of the recorded data using the following script (using from_caliperreader based on #161):

#! /usr/bin/env python3

import hatchet as ht

if __name__ == '__main__':
    gf = ht.GraphFrame.from_caliperreader('sample_profile.cali')
    print(gf.tree())

This resulted in the following error:

Traceback (most recent call last):
  File "/u/ydfb4q/.pyenv/versions/3.8.5/lib/python3.8/site-packages/pandas/core/indexes/base.py", line 3653, in get_loc
    return self._engine.get_loc(casted_key)
  File "pandas/_libs/index.pyx", line 147, in pandas._libs.index.IndexEngine.get_loc
  File "pandas/_libs/index.pyx", line 176, in pandas._libs.index.IndexEngine.get_loc
  File "pandas/_libs/hashtable_class_helper.pxi", line 7080, in pandas._libs.hashtable.PyObjectHashTable.get_item
  File "pandas/_libs/hashtable_class_helper.pxi", line 7088, in pandas._libs.hashtable.PyObjectHashTable.get_item
KeyError: Node({'name': 'main', 'type': 'function'})

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "./hatchet_test.py", line 9, in <module>
    print(gf.tree())
  File "/u/ydfb4q/.pyenv/versions/3.8.5/lib/python3.8/site-packages/hatchet/util/deprecated.py", line 14, in wrapper
    return f(*args, **kwargs)
  File "/u/ydfb4q/.pyenv/versions/3.8.5/lib/python3.8/site-packages/hatchet/graphframe.py", line 1050, in tree
    return ConsoleRenderer(unicode=unicode, color=color).render(
  File "/u/ydfb4q/.pyenv/versions/3.8.5/lib/python3.8/site-packages/hatchet/external/console.py", line 153, in render
    result += self.render_frame(root, dataframe)
  File "/u/ydfb4q/.pyenv/versions/3.8.5/lib/python3.8/site-packages/hatchet/external/console.py", line 264, in render_frame
    node_metric = dataframe.loc[df_index, self.primary_metric]
  File "/u/ydfb4q/.pyenv/versions/3.8.5/lib/python3.8/site-packages/pandas/core/indexing.py", line 1097, in __getitem__
    return self._getitem_tuple(key)
  File "/u/ydfb4q/.pyenv/versions/3.8.5/lib/python3.8/site-packages/pandas/core/indexing.py", line 1280, in _getitem_tuple
    return self._getitem_lowerdim(tup)
  File "/u/ydfb4q/.pyenv/versions/3.8.5/lib/python3.8/site-packages/pandas/core/indexing.py", line 1000, in _getitem_lowerdim
    section = self._getitem_axis(key, axis=i)
  File "/u/ydfb4q/.pyenv/versions/3.8.5/lib/python3.8/site-packages/pandas/core/indexing.py", line 1343, in _getitem_axis
    return self._get_label(key, axis=axis)
  File "/u/ydfb4q/.pyenv/versions/3.8.5/lib/python3.8/site-packages/pandas/core/indexing.py", line 1293, in _get_label
    return self.obj.xs(label, axis=axis)
  File "/u/ydfb4q/.pyenv/versions/3.8.5/lib/python3.8/site-packages/pandas/core/generic.py", line 4095, in xs
    loc = index.get_loc(key)
  File "/u/ydfb4q/.pyenv/versions/3.8.5/lib/python3.8/site-packages/pandas/core/indexes/base.py", line 3655, in get_loc
    raise KeyError(key) from err
KeyError: Node({'name': 'main', 'type': 'function'})

Start with the from_caliperreader call in the supplied script and trace how the attached sample_profile.cali file becomes a GraphFrame. Then inspect GraphFrame.tree() and the console renderer at the traceback's external/console.py entry point. Done means the sample profile can be loaded and its tree rendered without the reported KeyError.