<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_source_snapshots(self, snapshot, fallback_self=False):
 """ Get list of source snapshot names of given snapshot TODO: we have to decide by description at the moment """

        if not snapshot:
            return []

        source_snapshots = re.findall(r"'([\w\d\.-]+)'", snapshot['Description'])
        if not source_snapshots and fallback_self:
            source_snapshots = [snapshot['Name']]

        source_snapshots.sort()
        return source_snapshots