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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 _read_plain(self, lines):
 """ Read text fragments from a plain format text file. :param list lines: the lines of the plain text file :param dict parameters: additional parameters for parsing (e.g., class/id regex strings) :raises: ValueError: if the id regex is not valid """

        self.log(u"Parsing fragments from plain text format")
        id_format = self._get_id_format()
        lines = [line.strip() for line in lines]
        pairs = []
        i = 1
        for line in lines:
            identifier = id_format % i
            text = line.strip()
            pairs.append((identifier, [text]))
            i += 1
        self._create_text_fragments(pairs)