How to use the unidiff.patch.Line function in unidiff

def setUp(self):
        super(TestHunk, self).setUp()
        self.context_line = Line('Sample line', line_type=LINE_TYPE_CONTEXT)
        self.added_line = Line('Sample line', line_type=LINE_TYPE_ADDED)
        self.removed_line = Line('Sample line', line_type=LINE_TYPE_REMOVED)

def setUp(self):
        super(TestHunk, self).setUp()
        self.context_line = Line('Sample line', line_type=LINE_TYPE_CONTEXT)
        self.added_line = Line('Sample line', line_type=LINE_TYPE_ADDED)
        self.removed_line = Line('Sample line', line_type=LINE_TYPE_REMOVED)

def setUp(self):
        super(TestHunk, self).setUp()
        self.context_line = Line('Sample line', line_type=LINE_TYPE_CONTEXT)
        self.added_line = Line('Sample line', line_type=LINE_TYPE_ADDED)
        self.removed_line = Line('Sample line', line_type=LINE_TYPE_REMOVED)

def __init__(self, value, line_type,
                 source_line_no=None, target_line_no=None, diff_line_no=None):
        super(Line, self).__init__()
        self.source_line_no = source_line_no
        self.target_line_no = target_line_no
        self.diff_line_no = diff_line_no
        self.line_type = line_type
        self.value = value

def _parse_hunk(diff, source_start, source_len, target_start, target_len,
                section_header):
    """Parse a diff hunk details."""
    hunk = Hunk(source_start, source_len, target_start, target_len,
                section_header)
    source_line_no = hunk.source_start
    target_line_no = hunk.target_start

    for line in diff:
        valid_line = RE_HUNK_BODY_LINE.match(line)
        if not valid_line:
            raise UnidiffParseError('Hunk diff line expected: %s' % line)

        line_type = valid_line.group('line_type')
        value = valid_line.group('value')
        original_line = Line(value, line_type=line_type)
        if line_type == LINE_TYPE_ADDED:
            original_line.target_line_no = target_line_no
            target_line_no += 1
        elif line_type == LINE_TYPE_REMOVED:
            original_line.source_line_no = source_line_no
            source_line_no += 1
        elif line_type == LINE_TYPE_CONTEXT:
            original_line.target_line_no = target_line_no
            target_line_no += 1
            original_line.source_line_no = source_line_no
            source_line_no += 1
        else:
            original_line = None

        if original_line:
            hunk.append(original_line)

for diff_line_no, line in diff:
            if encoding is not None:
                line = line.decode(encoding)

            valid_line = RE_HUNK_BODY_LINE.match(line)
            if not valid_line:
                valid_line = RE_HUNK_EMPTY_BODY_LINE.match(line)

            if not valid_line:
                raise UnidiffParseError('Hunk diff line expected: %s' % line)

            line_type = valid_line.group('line_type')
            if line_type == LINE_TYPE_EMPTY:
                line_type = LINE_TYPE_CONTEXT
            value = valid_line.group('value')
            original_line = Line(value, line_type=line_type)
            if line_type == LINE_TYPE_ADDED:
                original_line.target_line_no = target_line_no
                target_line_no += 1
            elif line_type == LINE_TYPE_REMOVED:
                original_line.source_line_no = source_line_no
                source_line_no += 1
            elif line_type == LINE_TYPE_CONTEXT:
                original_line.target_line_no = target_line_no
                target_line_no += 1
                original_line.source_line_no = source_line_no
                source_line_no += 1
            elif line_type == LINE_TYPE_NO_NEWLINE:
                pass
            else:
                original_line = None