Add a model instance to the application model pool.

        :param moduleName: <str> module name in which the model is located
        :param modelName: <str> model name
        :param model: <object> model instance
        :return: <void>

def addModel(self, moduleName, modelName, model):
        """
        Add a model instance to the application model pool.

        :param moduleName: <str> module name in which the model is located
        :param modelName: <str> model name
        :param model: <object> model instance
        :return: <void>
        """
        modelIdentifier = "{}.{}".format(moduleName, modelName)
        if modelIdentifier not in self._models:
            self._models[modelIdentifier] = model
        else:
            message = "Application - addModel() - " \
                      "A model with the identifier {} already exists." \
                      .format(modelIdentifier)
            raise Exception(message)