def assert_contains_lines(self, lines2: Sequence[str]) -> None:
        """Assert that ``lines2`` are contained (linearly) in :attr:`stringio`'s value.

        Lines are matched using :func:`LineMatcher.fnmatch_lines <pytest.LineMatcher.fnmatch_lines>`.
        """
        __tracebackhide__ = True
        val = self.stringio.getvalue()
        self.stringio.truncate(0)
        self.stringio.seek(0)
        lines1 = val.split("\n")
        LineMatcher(lines1).fnmatch_lines(lines2)
Assert that ``lines2`` are contained (linearly) in :attr:`stringio`'s value.

        Lines are matched using :func:`LineMatcher.fnmatch_lines <pytest.LineMatcher.fnmatch_lines>`.
        
src/_pytest/pytester.py