deepaas-cli always expects get_predict_args() and get_train_args()

[vykozlov]

Description

Some AI models provide only prediction, therefore "get_train_args()" function does not exist. It does not cause an error in deepaas-run but deepaas-cli by default always expects both of the "get_train_args()" and "get_predict_args()" to be present.

Steps to Reproduce

1. in a AI module comment "get_train_args()"
2. call deepaas-cli predict --help
3. see error as e.g.

train_args = _fields_to_dict(model_obj.get_train_args())
                                ^^^^^^^^^^^^^^^^^^^^^^^^
AttributeError: module 'zooprocess_multiple_separator.api' has no attribute 'get_train_args'. Did you mean: 'get_predict_args'?

Expected behavior:

deepaas-cli is able to deal with cases when only predict() or train() is available

Versions

DEEPaaS API 2.5.2 and earlier