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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def format_active_subjects(request):
 """Create a string listing active subjects for this connection, suitable for appending to authentication error messages."""

    decorated_subject_list = [request.primary_subject_str + ' (primary)']
    for subject in request.all_subjects_set:
        if subject != request.primary_subject_str:
            decorated_subject_list.append(subject)
    return ', '.join(decorated_subject_list)