[Wiggo]

I have a column #series authors (thx chaley)

Spoiler:

python:
def evaluate(book, context):
    if book.series is None:
        return ''
    db = context.db.new_api
    ans = set()
    # Get the list of books in the series
    ids = db.search(f'series:"={book.series}"', '')
    if ids:
        # Get all the author_sort values for the books in the series
        author_sorts = (v for v in db.all_field_for('author_sort', ids).values())
        # Add the names to the result set, removing duplicates
        for aus in author_sorts:
            ans.update(v.strip() for v in aus.split('&'))
    # Make a sorted comma-separated string from the result set
    return ', '.join(v.replace(',', ';') for v in sorted(ans))

And I have a column symbol for more than one series author

program:
	if list_count($#series_authors, ',') > 1 then
		'series_authors.png'
	fi

I wanted to replace list_count by list_count_field but I get an error

program:
	if list_count_field('#series_authors') > 1 then
		'series_authors.png'
	fi

I installed Calibre 7.20.100 but as always, I have no idea.