import dbus
import json
bus = dbus.SessionBus()

# Create an object that will proxy for a particular remote object.
remote_object = bus.get_object("org.mpris.MediaPlayer2.GnomeMusic", # Connection name
                               "/org/mpris/MediaPlayer2" # Object's path
                              )

iface = dbus.Interface(remote_object, 'org.freedesktop.DBus.Properties')
msg = (json.dumps(iface.Get("org.mpris.MediaPlayer2.Player", "Metadata"), indent=0))
print msg