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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 _get_aliases(self):
 u"""Creates a dict with aliases. The key is a normalized tagname, value the original tagname. """

        if self._aliases is None:
            self._aliases = {}

            if self._xml is not None:
                for child in self._xml.iterchildren():
                    self._aliases[helpers.normalize_tag(child.tag)] = child.tag

        return self._aliases