How to use the py.io function in py

def runtest(self):
        call = py.io.StdCapture.call
        found_errors, out, err = call(
            check_file,
            self.fspath,
            self.flake8ignore,
            self.maxlength,
            self.maxcomplexity,
            self.showshource,
            self.statistics)
        if found_errors:
            raise Flake8Error(out, err)
        # update mtime only if test passed
        # otherwise failures would not be re-run next time
        if hasattr(self.config, "_flake8mtimes"):
            self.config._flake8mtimes[str(self.fspath)] = (self._flake8mtime,
                                                           self.flake8ignore)

def pickletest(mod):
    f1 = py.io.TextIO()
    f2 = py.io.TextIO()

    pickler1 = mod.Pickler(f1)
    unpickler1 = mod.Unpickler(f2)

    pickler2 = mod.Pickler(f2)
    unpickler2 = mod.Unpickler(f1)

    #pickler1.memo = unpickler1.memo = {}
    #pickler2.memo = unpickler2.memo = {}

    d = {}

    pickler1.dump(d)
    f1.seek(0)
    d_other = unpickler2.load()

def _notin_text(term, text):
    index = text.find(term)
    head = text[:index]
    tail = text[index+len(term):]
    correct_text = head + tail
    diff = _diff_text(correct_text, text)
    newdiff = ['%s is contained here:' % py.io.saferepr(term, maxsize=42)]
    for line in diff:
        if line.startswith('Skipping'):
            continue
        if line.startswith('- '):
            continue
        if line.startswith('+ '):
            newdiff.append('  ' + line[2:])
        else:
            newdiff.append(line)
    return newdiff

def test_stdouterrin_setnull():
    cap = py.io.StdCaptureFD()
    from py.__.execnet.register import stdouterrin_setnull
    stdouterrin_setnull()
    import os
    os.write(1, "hello")
    if os.name == "nt":
        os.write(2, "world")
    os.read(0, 1)
    out, err = cap.reset()
    assert not out
    assert not err

assert link.href.endswith("/pkg1-2.6.tgz")
    # we check here that the upload of docs without version was
    # automatically tied to the newest release metadata
    link = vv.get_link(rel="doczip")
    history_log = link.log
    assert len(history_log) == 2
    assert history_log[0]['what'] == 'upload'
    assert history_log[0]['who'] == 'user1'
    assert history_log[0]['dst'] == 'user1/dev'
    assert history_log[1]['what'] == 'push'
    assert history_log[1]['who'] == 'user1'
    assert history_log[1]['src'] == 'user1/dev'
    assert history_log[1]['dst'] == 'user2/prod'
    assert link.href.endswith("/pkg1-2.6.doc.zip")
    r = testapp.get(link.href)
    archive = Archive(py.io.BytesIO(r.body))
    assert 'index.html' in archive.namelist()

    # reconfigure inheritance and see if get shadowing information
    mapp.modify_index("user1/dev", indexconfig=dict(bases=("/user2/prod",)))
    vv = get_view_version_links(testapp, "/user1/dev", "pkg1", "2.6", proj=proj)
    link = vv.get_link(rel="releasefile")
    assert link.href.endswith("/pkg1-2.6.tgz")
    shadows = vv.shadowed()
    assert len(shadows) == 1, vv.versiondata
    vv = shadows[0]
    link = vv.get_link(rel="releasefile")
    assert link.href.endswith("/pkg1-2.6.tgz")

def _saferepr(self, obj):
        return py.io.saferepr(obj)

def test_stdouterrin_setnull():
    cap = py.io.StdCaptureFD()
    from py.__.execnet.gateway import stdouterrin_setnull
    stdouterrin_setnull()
    import os
    os.write(1, "hello".encode('ascii'))
    if os.name == "nt":
        os.write(2, "world")
    os.read(0, 1)
    out, err = cap.reset()
    assert not out
    assert not err

def pretty_print(self):
        tw = py.io.TerminalWriter()
        if self.layer_name == self.DATA_LAYER:
            tw.write('DATA')
            return

        tw.write('Layer %s:' % self.layer_name.upper() + os.linesep, yellow=True, bold=True)
        for field_line in self._get_all_field_lines():
            if ':' in field_line:
                field_name, field_line = field_line.split(':', 1)
                tw.write(field_name + ':', green=True, bold=True)
            tw.write(field_line, bold=True)

def __init__(self, name, justification=20):
        self.justification = justification
        self.name = name
        self.op_code = None
        self.bar = progress(self.name, _translate(None), 10, just=self.justification)
        res, out, self._err = py.io.StdCaptureFD.call(self.bar.start)

if not config.path_nodeinfo.exists():
            fatal("The path '%s' contains no devpi-server data, use devpi-init to initialize." % config.serverdir)

    if args.init or args.import_:
        sdir = config.serverdir
        if not (sdir.exists() and len(sdir.listdir()) >= 2):
            set_state_version(config, DATABASE_VERSION)

    xom = xom_from_config(config)

    init_default_indexes(xom)

    if args.start or args.stop or args.log or args.status:
        xprocdir = config.serverdir.join(".xproc")
        from devpi_server.bgserver import BackgroundServer
        tw = py.io.TerminalWriter()
        bgserver = BackgroundServer(tw, xprocdir)
        if args.start:
            return bgserver.start(args, argv[1:])
        elif args.stop:
            return bgserver.stop()
        elif args.log:
            return bgserver.log()
        elif args.status:
            if bgserver.info.isrunning():
                bgserver.line("server is running with pid %s" %
                              bgserver.info.pid)
            else:
                bgserver.line("no server is running")
            return

    if args.passwd: