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

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)