Converting `MatrixTable` entry to column field

I have a MatrixTable that I created with the Table.to_matrix_table() method. However, I forgot to list a column field such that it now became an entry. Creating this table takes the better part of a day on my desktop, so I’m loath to re-run the script.

Is there a way to convert an entry to a column field in an existing MatrixTable? I tried converting the MatrixTable back to a table with mt.make_table(), but that ran into a Python RecursionError.

If it should be a column field, that means that the field has the same value for each entry per column. So you can safely do something like:

col_field_name = '???'
col_field_name_old = f'{col_field_name}_old'
mt = mt.rename({col_field_name: col_field_name_old})
mt = mt.annotate_cols(**{col_field_name: hl.agg.take(mt[col_field_name_old], 1)[0])
mt = mt.drop(col_field_name_old)