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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 populate_from_settings(self):
 """ Populate the aliases from the ``THUMBNAIL_ALIASES`` setting. """

        settings_aliases = settings.THUMBNAIL_ALIASES
        if settings_aliases:
            for target, aliases in settings_aliases.items():
                target_aliases = self._aliases.setdefault(target, {})
                target_aliases.update(aliases)