<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def get_author_label(self, urn):
 """Get the label corresponding to the author identified by the CTS URN. try to get an lang=en label (if multiple labels in this lang pick the shortest) try to get a lang=la label (if multiple labels in this lang exist pick the shortest) try to get a lang=None label (if multiple labels in this lang exist pick the shortest) returns None if no name is found """

        author = self.get_resource_by_urn(urn)
        names = author.get_names()
        en_names = sorted([name[1] for name in names if name[0] == "en"], key=len)
        try:
            assert len(en_names) > 0
            return en_names[0]
        except Exception as e:
            none_names = sorted([name[1] for name in names if name[0] == None], key=len)
            try:
                return none_names[0]
            except Exception as e:
                la_names = sorted([name[1] for name in names if name[0] == "la"], key=len)
                try:
                    assert len(la_names) > 0
                    return la_names[0]
                except Exception as e:
                    return None