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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_author_line(author_names):
 """authorLine format depends on if there is 1, 2 or more than 2 authors"""

    author_line = None
    if not author_names:
        return author_line
    if len(author_names) <= 2:
        author_line = ", ".join(author_names)
    elif len(author_names) > 2:
        author_line = author_names[0] + " et al."
    return author_line