human
I wrote the below code

    def sorter(value):
        return column_index_from_string(value[0])
    el = Element('cols')
    obj = None
    for (idx, col) in sorted(worksheet.column_dimensions.items(), key=sorter):
        if (dict(col) == {}):
            continue
        idx = column_index_from_string(idx)
        obj = Element('col', dict(col))
        obj.set('min', ('%d' % (col.min or idx)))
        obj.set('max', ('%d' % (col.max or idx)))
        el.append(obj)
    if (obj is not None):
        return el

What's a good function header?
assistant
#Here's a good function header.

def write_cols(worksheet):