How to use the gprof2dot.ParseError function in gprof2dot

def parse_subentry(self):
        entry = Struct()
        line = self.consume()
        mo = self.entry_re.match(line)
        if not mo:
            raise ParseError('failed to parse', line)
        fields = mo.groupdict()
        entry.samples = int(mo.group(1))
        if 'source' in fields and fields['source'] != '(no location information)':
            source = fields['source']
            filename, lineno = source.split(':')
            entry.filename = filename
            entry.lineno = int(lineno)
        else:
            source = ''
            entry.filename = None
            entry.lineno = None
        entry.image = fields.get('image', '')
        entry.application = fields.get('application', '')
        if 'symbol' in fields and fields['symbol'] != '(no symbols)':
            entry.symbol = fields['symbol']
        else: