How to use the gunicorn.six function in gunicorn

def parse_chunk_size(self, unreader, data=None):
        buf = six.BytesIO()
        if data is not None:
            buf.write(data)

        idx = buf.getvalue().find(b"\r\n")
        while idx < 0:
            self.get_data(unreader, buf)
            idx = buf.getvalue().find(b"\r\n")

        data = buf.getvalue()
        line, rest_chunk = data[:idx], data[idx + 2:]

        chunk_size = line.split(b";", 1)[0].strip()
        try:
            chunk_size = int(chunk_size, 16)
        except ValueError:
            raise InvalidChunkSize(chunk_size)

def getsize(self, size):
        if size is None:
            return six.MAXSIZE
        elif not isinstance(size, six.integer_types):
            raise TypeError("size must be an integral type")
        elif size < 0:
            return six.MAXSIZE
        return size

def _fileobj_to_fd(fileobj):
    """Return a file descriptor from a file object.

    Parameters:
    fileobj -- file object or file descriptor

    Returns:
    corresponding file descriptor

    Raises:
    ValueError if the object is invalid
    """
    if isinstance(fileobj, six.integer_types):
        fd = fileobj
    else:
        try:
            fd = int(fileobj.fileno())
        except (AttributeError, TypeError, ValueError):
            raise ValueError("Invalid file object: "
                             "{0!r}".format(fileobj))
    if fd < 0:
        raise ValueError("Invalid file descriptor: {0}".format(fd))
    return fd

respiter = self.wsgi(environ, resp.start_response)
            try:
                if isinstance(respiter, environ['wsgi.file_wrapper']):
                    resp.write_file(respiter)
                else:
                    for item in respiter:
                        resp.write(item)
                resp.close()
                request_time = datetime.now() - request_start
                self.log.access(resp, req, environ, request_time)
            finally:
                if hasattr(respiter, "close"):
                    respiter.close()
        except EnvironmentError:
            # pass to next try-except level
            six.reraise(*sys.exc_info())
        except Exception:
            if resp and resp.headers_sent:
                # If the requests have already been sent, we should close the
                # connection to indicate the error.
                self.log.exception("Error handling request")
                try:
                    client.shutdown(socket.SHUT_RDWR)
                    client.close()
                except EnvironmentError:
                    pass
                raise StopIteration()
            raise
        finally:
            try:
                self.cfg.post_request(self, req, environ, resp)
            except Exception:

# UN-marshal it.
        import marshal
        code_obj = marshal.loads(data[8:])

    elif result is PY_SOURCE:
        # This is a .py file.
        code_obj = compile(data, fullpath, 'exec')

    else:
        # Unsupported extension
        raise Exception("Input file is unknown format: {0}".format(fullpath))

    # Return code object
    return code_obj

if six.PY3:
    def execfile_(fname, *args):
        if fname.endswith(".pyc"):
            code = _get_codeobj(fname)
        else:
            code = compile(open(fname, 'rb').read(), fname, 'exec')
        return six.exec_(code, *args)

    def bytes_to_str(b):
        if isinstance(b, six.text_type):
            return b
        return str(b, 'latin1')

    import urllib.parse

    def unquote_to_wsgi_str(string):
        return _unquote_to_bytes(string).decode('latin-1')

def set(self, val):
        if not six.callable(self.validator):
            raise TypeError('Invalid validator: %s' % self.name)
        self.value = self.validator(val)

def __len__(self):
        return len(self._selector._fd_to_key)

    def __getitem__(self, fileobj):
        try:
            fd = self._selector._fileobj_lookup(fileobj)
            return self._selector._fd_to_key[fd]
        except KeyError:
            raise KeyError("{0!r} is not registered".format(fileobj))

    def __iter__(self):
        return iter(self._selector._fd_to_key)


class BaseSelector(six.with_metaclass(ABCMeta)):
    """Selector abstract base class.

    A selector supports registering file objects to be monitored for specific
    I/O events.

    A file object is a file descriptor or any object with a `fileno()` method.
    An arbitrary object can be attached to the file object, which can be used
    for example to store context information, a callback, etc.

    A selector can use various implementations (select(), poll(), epoll()...)
    depending on the platform. The default `Selector` class uses the most
    efficient implementation on the current platform.
    """

    @abstractmethod
    def register(self, fileobj, events, data=None):

default = None
    desc = """\
        Load a PasteDeploy config file. The argument may contain a ``#``
        symbol followed by the name of an app section from the config file,
        e.g. ``production.ini#admin``.

        At this time, using alternate server blocks is not supported. Use the
        command line arguments to control server configuration instead.
        """


class OnStarting(Setting):
    name = "on_starting"
    section = "Server Hooks"
    validator = validate_callable(1)
    type = six.callable

    def on_starting(server):
        pass
    default = staticmethod(on_starting)
    desc = """\
        Called just before the master process is initialized.

        The callable needs to accept a single instance variable for the Arbiter.
        """


class OnReload(Setting):
    name = "on_reload"
    section = "Server Hooks"
    validator = validate_callable(1)
    type = six.callable

self.wsgi = self.app.wsgi()
        except SyntaxError as e:
            if not self.cfg.reload:
                raise

            self.log.exception(e)

            # fix from PR #1228
            # storing the traceback into exc_tb will create a circular reference.
            # per https://docs.python.org/2/library/sys.html#sys.exc_info warning,
            # delete the traceback after use.
            try:
                _, exc_val, exc_tb = sys.exc_info()
                self.reloader.add_extra_file(exc_val.filename)

                tb_string = six.StringIO()
                traceback.print_tb(exc_tb, file=tb_string)
                self.wsgi = util.make_fail_app(tb_string.getvalue())
            finally:
                del exc_tb

def set(self, val):
        if not six.callable(self.validator):
            raise TypeError('Invalid validator: %s' % self.name)
        self.value = self.validator(val)