Pandas PerformanceWarning

[neubig]

When running Zeno the Zeno visualization functions (in the context of Zeno Build), I'm getting the following warnings:

zeno/util.py:86: PerformanceWarning: DataFrame is highly fragmented.  This is usually the result of calling `frame.insert` many times, which has poor performance.  Consider joining all columns at once using pd.concat(axis=1) instead. To get a de-fragmented frame, use `newframe = frame.copy()`
  df.loc[:, str(col_name)] = pd.Series([pd.NA] * df.shape[0], index=df.index)

And indeed, some operations seem slower than I expect. It might be nice to debug this.