How to use the tmuxp.Server function in tmuxp

def __enter__(self):
        self.tmux_config = self.tempfile(self.tmux_config_contents())
        self.bash_config = self.tempfile(self.bash_config_contents())

        self.server = tmuxp.Server()
        if self.use_existing_session:
            try:
                session_dict = self.server.attached_sessions()  # until tmuxp bug is fixed
                if session_dict is None:
                    raise tmuxp.exc.TmuxpException
                self.session = tmuxp.Session(self.server, **session_dict[0])
            except tmuxp.exc.TmuxpException:
                self.session = self.server.new_session(session_name='rlundotesting')
        else:
            self.session = self.server.new_session(session_name='rlundotesting', kill_session=True)

        self.window = self.session.new_window(attach=False)
        try:
            output = self.window.panes[0].cmd('respawn-pane', '-k', 'bash --rcfile %s --noprofile' % (self.bash_config.name, ))
            if output.stderr:
                raise ValueError(repr(output.stderr) + " " +  repr(self.window.panes))

session = tmux.list_sessions()[0]
            session.attach_session()
            exit(1)
        else:
            session = tmux.new_session(session_name="iscap")
            top_pane = session.attached_pane()
            tmux.cmd('split-window')
            new_pane = session.attached_pane()
            new_pane.clear()
            top_pane.select_pane()
            top_pane.clear()
            top_pane.send_keys('iscap')
            session.attach_session()
            exit(0)

    tmux = tmuxp.Server();
    return tmux

def setup_tmux():
    if not 'TMUX' in os.environ:
        tmux = tmuxp.Server();
        if tmux.has_session('iscap'):
            print ('error: iscap session already running. Try reattaching with `tmux attach`')
            session = tmux.list_sessions()[0]
            session.attach_session()
            exit(1)
        else:
            session = tmux.new_session(session_name="iscap")
            top_pane = session.attached_pane()
            tmux.cmd('split-window')
            new_pane = session.attached_pane()
            new_pane.clear()
            top_pane.select_pane()
            top_pane.clear()
            top_pane.send_keys('iscap')
            session.attach_session()
            exit(0)

import tmuxp
import pprint

server = tmuxp.Server()

def format_session(session):
    pane_count = [w.panes for w in session.windows]
    pane_count = [pane for window in pane_count for pane in window]
    pane_count = len(pane_count)
    return "({0}) {1} | {2} Windows, {3} Panes".format(
            session.get("session_id"),
            session.get("session_name"),
            session.get("session_windows"),
            pane_count)

def list_sessions():
    sessions = server.list_sessions()
    sessions = [format_session(s) for s in sessions]
    return sessions

:todo: initialize :class:`Session` from here, in ``self.session``.

        :param sconf: session config, includes a :py:obj:`list` of ``windows``.
        :type sconf: :py:obj:`dict`

        :param server:
        :type server: :class:`Server`

        """

        if not sconf:
            raise exc.EmptyConfigException('session configuration is empty.')

        # config.validate_schema(sconf)

        if isinstance(server, Server):
            self.server = server
        else:
            self.server = None

        self.sconf = sconf