<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def authors(self):
 """A list of scopus_api._ScopusAuthor objects."""

        authors = self.xml.find('authors', ns)
        try:
            return [_ScopusAuthor(author) for author in authors]
        except TypeError:
            return None