How to use the pdbpp.StringIO function in pdbpp

def test_help(command, expected_regex):
    instance = PdbTest()
    instance.stdout = StringIO()

    # Redirect sys.stdout because Python 2 pdb.py has `print >>self.stdout` for
    # some functions and plain ol' `print` for others.
    oldstdout = sys.stdout
    sys.stdout = instance.stdout
    try:
        instance.do_help(command)
    finally:
        sys.stdout = oldstdout

    output = instance.stdout.getvalue()
    assert re.search(expected_regex, output)