Multi-index columns all blank in Tabulator

[ahuang11]

import pandas as pd

df = pd.DataFrame({
    'time': pd.to_datetime(['2020-01-01 00:00:00'] * 50 + ['2020-01-01 00:30:00'] * 50),
    'value': range(100),
    'group': ['A', 'B'] * 50
})

# Aggregate values for duplicate time entries by taking the mean
df_agg = df.groupby(['time', 'group']).first().reset_index()
pivot_df = df_agg.pivot(index="time", columns="group", values=["value"])
import panel as pn
pn.extension()
display(pivot_df)
pn.widgets.Tabulator(pivot_df)

The work around is to set pivot_df.columns = pivot_df.columns.as_flat_index()