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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 _retrieve_page(self, page_index):
 """Returns the node of matches to be processed"""


        params = self._get_params()
        params["page"] = str(page_index)
        doc = self._request(self._ws_prefix + ".search", True, params)

        return doc.getElementsByTagName(self._ws_prefix + "matches")[0]