Get default shaman instance by "data/trained.json"

def default() :
		""" Get default shaman instance by "data/trained.json"
		"""
		if Shaman._default_instance is not None :
			return Shaman._default_instance

		with open((os.path.dirname(__file__) or '.') + '/data/trained.json') as file :
			tset = json.loads(file.read())

		Shaman._default_instance = Shaman(tset)
		return Shaman._default_instance