create an iterator over all documents in the file (i.e. all
        <text> elements).

        Once you have iterated over all documents, call this method again
        if you want to iterate over them again.

def _reset_corpus_iterator(self):
        """
        create an iterator over all documents in the file (i.e. all
        <text> elements).

        Once you have iterated over all documents, call this method again
        if you want to iterate over them again.
        """
        self.__context = etree.iterparse(self.urml_file, events=('end',),
                                         tag='document', recover=False)