import dbus

bus = dbus.SessionBus()
# I'd like to turn off introspection because I know the signature of the method
# I'm calling!
iface = dbus.Interface(
    bus.get_object(
        'org.freedesktop.Notifications',
        '/org/freedesktop/Notifications',
        introspect=False),
    'org.freedesktop.Notifications')

# But this:
iface.Notify('uk.me.wjt.example', 0, '', 'I <3 dbus-python', '(maybe)', [],
    {'foo': 3, 'bar': 'blah'}, 0,
    # susssussudio
    signature='susssasa{sv}u')
# yields this:
#
#     TypeError: call_blocking() got multiple values for keyword argument
#     'signature'
#
# While omitting the signature yields:
#
#     ValueError: Unable to guess signature from an empty list
#