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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_elements(self, source):
 """ Returns the list of HtmlElements for the source :param source: The source list to parse :type source: list :returns: A list of HtmlElements :rtype: list """

        return list(chain(*[self.tree.xpath(xpath) for xpath in source]))