code: def validate(self):
          
          from .files import AudioFile
          try:
              assert self.kind == content_kinds.AUDIO, "Assumption Failed: Node should be audio"
              assert self.questions == [], "Assumption Failed: Audio should not have questions"
              assert len(self.files) > 0, "Assumption Failed: Audio should have at least one file"
              assert any(filter(lambda f: isinstance(f, AudioFile), self.files)), "Assumption Failed: Audio should have at least one audio file"
              return super(AudioNode, self).validate()
          except AssertionError as ae:
              raise InvalidNodeException("Invalid node ({}): {} - {}".format(ae.args[0], self.title, self.__dict__))
docs: validate: Makes sure audio is valid
              Args: None
              Returns: boolean indicating if audio is valid