Python API: Check for application ready?

What changes will be made and why they would make a better Orfeo ToolBox?

In Python/(C++?) API(s), it could be great to have a check that an application has been Execute()-ed Beginners that forget to Execute() their application face a cryptic Segmentation fault

High level description

Add a check to prevent a pipeline initializing from no-ready apps

Risks and benefits

Help users of Python API

Alternatives for implementations

I don't know. Maybe this could be done directly in the C++ API, benefiting also C++.

Who will be developing the proposed changes?

For now it's just a discussion. Maybe its too complicated? I don't know well the app chaining stuff