gi.repository Gst problems

I am writing a simple script to play an audio file with the Gst (gstreamer) library of PyGobject, when executing the script the following error is displayed:

  

(python3: 31506): GStreamer-CRITICAL **: 00: 55: 27.705: Trying to   dispose element pipeline, but it is in READY instead of the NULL   state. You need to explicitly set elements to the NULL state before   dropping the final reference, to allow them to clean up. This problem   may also be caused by a refcounting bug in the application or some   element.

     

(python3: 31506): GStreamer-CRITICAL **: 00: 55: 27.705: Trying to   dispose element audio_source, but it is in PAUSED instead of the NULL   state. You need to explicitly set elements to the NULL state before   dropping the final reference, to allow them to clean up. This problem   may also be caused by a refcounting bug in the application or some   element.

     

(python3: 31506): GStreamer-CRITICAL **: 00: 55: 27.705: Trying to   dispose element typefind, but it is in PAUSED instead of the NULL   state. You need to explicitly set elements to the NULL state before   dropping the final reference, to allow them to clean up. This problem   may also be caused by a refcounting bug in the application or some   element.

     

(python3: 31506): GStreamer-CRITICAL **: 00: 55: 27.705: Trying to   dispose element decode, but it is in PAUSED instead of the NULL state.   You need to explicitly set elements to the NULL state before dropping   The final reference, to allow them to clean up. This problem may also   be caused by a refcounting bug in the application or some element.

     

(python3: 31506): GStreamer-CRITICAL **: 00: 55: 27.706: Trying to   dispose element convert, but it is in PAUSED instead of the NULL   state. You need to explicitly set elements to the NULL state before   dropping the final reference, to allow them to clean up. This problem   may also be caused by a refcounting bug in the application or some   element.

     

(python3: 31506): GStreamer-CRITICAL **: 00: 55: 27.706: Trying to   dispose element audio_sink, but it is in PAUSED instead of the NULL   state. You need to explicitly set elements to the NULL state before   dropping the final reference, to allow them to clean up. This problem   may also be caused by a refcounting bug in the application or some   element.

I do not get any information about it, here's the Code of my script:

import gi
gi.require_version('Gst', '1.0')
from gi.repository import GObject, Gst

class SimplePlayer:

    def __init__(self, path):

        self.path = path

        # Init Gst
        GObject.threads_init()
        Gst.init(None)

        #Create Pipeline
        self.pipeline = Gst.Pipeline('pipeline')

        #Create Elements for Pipeline
        self.source = Gst.ElementFactory.make('filesrc', 'audio_source')
        self.decode = Gst.ElementFactory.make('decodebin', 'decode')
        self.audioconvert = Gst.ElementFactory.make('audioconvert', 'convert')
        self.audio_sink = Gst.ElementFactory.make('autoaudiosink', 'audio_sink')

        #Configure Elemnts
        self.source.set_property('location', path)

        #Adding Elements to Pipeline
        self.pipeline.add(self.source)
        self.pipeline.add(self.decode)
        self.pipeline.add(self.audioconvert)
        self.pipeline.add(self.audio_sink)


        #Linking Elements
        self.source.link(self.decode)
        self.decode.link(self.audioconvert)
        self.audioconvert.link(self.audio_sink)

        # Finally Playing =D
        self.pipeline.set_state(Gst.State.PLAYING)

        #I don't know well from here
        bus = self.pipeline.get_bus()
        msg = bus.timed_pop_filtered(Gst.CLOCK_TIME_NONE,Gst.MessageType.ERROR | Gst.MessageType.EOS)
        print(msg)

player = SimplePlayer('/home/user/Music/audio.mp3')

Also if you can suggest a tutorial for this library, it would be very useful for me. Thanks