from docker.api import APIClient
from docker.errors import APIError
from .resource import Model


class Swarm(Model):
    """
    The server's Swarm state. This a singleton that must be reloaded to get
    the current state of the Swarm.
    """
    id_attribute = 'ID'

    def __init__(self, *args, **kwargs):
        super(Swarm, self).__init__(*args, **kwargs)
        if self.client:
            try:
                self.reload()
            except APIError as e:
                # FIXME: https://github.com/docker/docker/issues/29192
                if e.response.status_code not in (406, 503):
                    raise

    @property
    def version(self):
        """
        The version number of the swarm. If this is not the same as the
        server, the :py:meth:`update` function will not work and you will
        need to call :py:meth:`reload` before calling it again.
        """
        return self.attrs.get('Version').get('Index')

    def get_unlock_key(self):
        return self.client.api.get_unlock_key()
    get_unlock_key.__doc__ = APIClient.get_unlock_key.__doc__

    def init(self, advertise_addr=None, listen_addr='0.0.0.0:2377',
             force_new_cluster=False, **kwargs):
        """
        Initialize a new swarm on this Engine.

        Args:
            advertise_addr (str): Externally reachable address advertised to
                other nodes. This can either be an address/port combination in
                the form ``192.168.1.1:4567``, or an interface followed by a
                port number, like ``eth0:4567``. If the port number is omitted,
                the port number from the listen address is used.

                If not specified, it will be automatically detected when
                possible.
            listen_addr (str): Listen address used for inter-manager
                communication, as well as determining the networking interface
                used for the VXLAN Tunnel Endpoint (VTEP). This can either be
                an address/port combination in the form ``192.168.1.1:4567``,
                or an interface followed by a port number, like ``eth0:4567``.
                If the port number is omitted, the default swarm listening port
                is used. Default: ``0.0.0.0:2377``
            force_new_cluster (bool): Force creating a new Swarm, even if
                already part of one. Default: False
            task_history_retention_limit (int): Maximum number of tasks
                history stored.
            snapshot_interval (int): Number of logs entries between snapshot.
            keep_old_snapshots (int): Number of snapshots to keep beyond the
                current snapshot.
            log_entries_for_slow_followers (int): Number of log entries to
                keep around to sync up slow followers after a snapshot is
                created.
            heartbeat_tick (int): Amount of ticks (in seconds) between each
                heartbeat.
            election_tick (int): Amount of ticks (in seconds) needed without a
                leader to trigger a new election.
            dispatcher_heartbeat_period (int):  The delay for an agent to send
                a heartbeat to the dispatcher.
            node_cert_expiry (int): Automatic expiry for nodes certificates.
            external_ca (dict): Configuration for forwarding signing requests
                to an external certificate authority. Use
                ``docker.types.SwarmExternalCA``.
            name (string): Swarm's name
            labels (dict): User-defined key/value metadata.
            signing_ca_cert (str): The desired signing CA certificate for all
                swarm node TLS leaf certificates, in PEM format.
            signing_ca_key (str): The desired signing CA key for all swarm
                node TLS leaf certificates, in PEM format.
            ca_force_rotate (int): An integer whose purpose is to force swarm
                to generate a new signing CA certificate and key, if none have
                been specified.
            autolock_managers (boolean): If set, generate a key and use it to
                lock data stored on the managers.
            log_driver (DriverConfig): The default log driver to use for tasks
                created in the orchestrator.

        Returns:
            ``True`` if the request went through.

        Raises:
            :py:class:`docker.errors.APIError`
                If the server returns an error.

        Example:

            >>> client.swarm.init(
                advertise_addr='eth0', listen_addr='0.0.0.0:5000',
                force_new_cluster=False, snapshot_interval=5000,
                log_entries_for_slow_followers=1200
            )

        """
        init_kwargs = {
            'advertise_addr': advertise_addr,
            'listen_addr': listen_addr,
            'force_new_cluster': force_new_cluster
        }
        init_kwargs['swarm_spec'] = self.client.api.create_swarm_spec(**kwargs)
        self.client.api.init_swarm(**init_kwargs)
        self.reload()

    def join(self, *args, **kwargs):
        return self.client.api.join_swarm(*args, **kwargs)
    join.__doc__ = APIClient.join_swarm.__doc__

    def leave(self, *args, **kwargs):
        return self.client.api.leave_swarm(*args, **kwargs)
    leave.__doc__ = APIClient.leave_swarm.__doc__

    def reload(self):
        """
        Inspect the swarm on the server and store the response in
        :py:attr:`attrs`.

        Raises:
            :py:class:`docker.errors.APIError`
                If the server returns an error.
        """
        self.attrs = self.client.api.inspect_swarm()

    def unlock(self, key):
        return self.client.api.unlock_swarm(key)
    unlock.__doc__ = APIClient.unlock_swarm.__doc__

    def update(self, rotate_worker_token=False, rotate_manager_token=False,
               **kwargs):
        """
        Update the swarm's configuration.

        It takes the same arguments as :py:meth:`init`, except
        ``advertise_addr``, ``listen_addr``, and ``force_new_cluster``. In
        addition, it takes these arguments:

        Args:
            rotate_worker_token (bool): Rotate the worker join token. Default:
                ``False``.
            rotate_manager_token (bool): Rotate the manager join token.
                Default: ``False``.

        Raises:
            :py:class:`docker.errors.APIError`
                If the server returns an error.

        """
        # this seems to have to be set
        if kwargs.get('node_cert_expiry') is None:
            kwargs['node_cert_expiry'] = 7776000000000000

        return self.client.api.update_swarm(
            version=self.version,
            swarm_spec=self.client.api.create_swarm_spec(**kwargs),
            rotate_worker_token=rotate_worker_token,
            rotate_manager_token=rotate_manager_token
        )

docker/models/swarm.py
from docker.api import APIClient
from docker.errors import APIError
from .resource import Model


class Swarm(Model):
    """
    The server's Swarm state. This a singleton that must be reloaded to get
    the current state of the Swarm.
    """
    id_attribute = 'ID'

    def __init__(self, *args, **kwargs):
        super(Swarm, self).__init__(*args, **kwargs)
        if self.client:
            try:
                self.reload()
            except APIError as e:
                # FIXME: https://github.com/docker/docker/issues/29192
                if e.response.status_code not in (406, 503):
                    raise

    @property
    def version(self):
        """
        The version number of the swarm. If this is not the same as the
        server, the :py:meth:`update` function will not work and you will
        need to call :py:meth:`reload` before calling it again.
        """
        return self.attrs.get('Version').get('Index')

    def get_unlock_key(self):
        return self.client.api.get_unlock_key()
    get_unlock_key.__doc__ = APIClient.get_unlock_key.__doc__

    def init(self, advertise_addr=None, listen_addr='0.0.0.0:2377',
             force_new_cluster=False, **kwargs):
        """
        Initialize a new swarm on this Engine.

        Args:
            advertise_addr (str): Externally reachable address advertised to
                other nodes. This can either be an address/port combination in
                the form ``192.168.1.1:4567``, or an interface followed by a
                port number, like ``eth0:4567``. If the port number is omitted,
                the port number from the listen address is used.

                If not specified, it will be automatically detected when
                possible.
            listen_addr (str): Listen address used for inter-manager
                communication, as well as determining the networking interface
                used for the VXLAN Tunnel Endpoint (VTEP). This can either be
                an address/port combination in the form ``192.168.1.1:4567``,
                or an interface followed by a port number, like ``eth0:4567``.
                If the port number is omitted, the default swarm listening port
                is used. Default: ``0.0.0.0:2377``
            force_new_cluster (bool): Force creating a new Swarm, even if
                already part of one. Default: False
            task_history_retention_limit (int): Maximum number of tasks
                history stored.
            snapshot_interval (int): Number of logs entries between snapshot.
            keep_old_snapshots (int): Number of snapshots to keep beyond the
                current snapshot.
            log_entries_for_slow_followers (int): Number of log entries to
                keep around to sync up slow followers after a snapshot is
                created.
            heartbeat_tick (int): Amount of ticks (in seconds) between each
                heartbeat.
            election_tick (int): Amount of ticks (in seconds) needed without a
                leader to trigger a new election.
            dispatcher_heartbeat_period (int):  The delay for an agent to send
                a heartbeat to the dispatcher.
            node_cert_expiry (int): Automatic expiry for nodes certificates.
            external_ca (dict): Configuration for forwarding signing requests
                to an external certificate authority. Use
                ``docker.types.SwarmExternalCA``.
            name (string): Swarm's name
            labels (dict): User-defined key/value metadata.
            signing_ca_cert (str): The desired signing CA certificate for all
                swarm node TLS leaf certificates, in PEM format.
            signing_ca_key (str): The desired signing CA key for all swarm
                node TLS leaf certificates, in PEM format.
            ca_force_rotate (int): An integer whose purpose is to force swarm
                to generate a new signing CA certificate and key, if none have
                been specified.
            autolock_managers (boolean): If set, generate a key and use it to
                lock data stored on the managers.
            log_driver (DriverConfig): The default log driver to use for tasks
                created in the orchestrator.

        Returns:
            ``True`` if the request went through.

        Raises:
            :py:class:`docker.errors.APIError`
                If the server returns an error.

        Example:

            >>> client.swarm.init(
                advertise_addr='eth0', listen_addr='0.0.0.0:5000',
                force_new_cluster=False, snapshot_interval=5000,
                log_entries_for_slow_followers=1200
            )

        """
        init_kwargs = {
            'advertise_addr': advertise_addr,
            'listen_addr': listen_addr,
            'force_new_cluster': force_new_cluster
        }
        init_kwargs['swarm_spec'] = self.client.api.create_swarm_spec(**kwargs)
        self.client.api.init_swarm(**init_kwargs)
        self.reload()
        return True

    def join(self, *args, **kwargs):
        return self.client.api.join_swarm(*args, **kwargs)
    join.__doc__ = APIClient.join_swarm.__doc__

    def leave(self, *args, **kwargs):
        return self.client.api.leave_swarm(*args, **kwargs)
    leave.__doc__ = APIClient.leave_swarm.__doc__

    def reload(self):
        """
        Inspect the swarm on the server and store the response in
        :py:attr:`attrs`.

        Raises:
            :py:class:`docker.errors.APIError`
                If the server returns an error.
        """
        self.attrs = self.client.api.inspect_swarm()

    def unlock(self, key):
        return self.client.api.unlock_swarm(key)
    unlock.__doc__ = APIClient.unlock_swarm.__doc__

    def update(self, rotate_worker_token=False, rotate_manager_token=False,
               **kwargs):
        """
        Update the swarm's configuration.

        It takes the same arguments as :py:meth:`init`, except
        ``advertise_addr``, ``listen_addr``, and ``force_new_cluster``. In
        addition, it takes these arguments:

        Args:
            rotate_worker_token (bool): Rotate the worker join token. Default:
                ``False``.
            rotate_manager_token (bool): Rotate the manager join token.
                Default: ``False``.

        Raises:
            :py:class:`docker.errors.APIError`
                If the server returns an error.

        """
        # this seems to have to be set
        if kwargs.get('node_cert_expiry') is None:
            kwargs['node_cert_expiry'] = 7776000000000000

        return self.client.api.update_swarm(
            version=self.version,
            swarm_spec=self.client.api.create_swarm_spec(**kwargs),
            rotate_worker_token=rotate_worker_token,
            rotate_manager_token=rotate_manager_token
        )

docker/models/swarm.py
diff --git a/docker/models/swarm.py b/docker/models/swarm.py
index 7396e730d..3a02ae370 100644
--- a/docker/models/swarm.py
+++ b/docker/models/swarm.py
@@ -112,6 +112,7 @@ def init(self, advertise_addr=None, listen_addr='0.0.0.0:2377',
         init_kwargs['swarm_spec'] = self.client.api.create_swarm_spec(**kwargs)
         self.client.api.init_swarm(**init_kwargs)
         self.reload()
+        return True
 
     def join(self, *args, **kwargs):
         return self.client.api.join_swarm(*args, **kwargs)

swarm.init() does not return a value
No return value unlike as specified in documentation. 
