Support several mocks of the same API method in the testing framework

[popescu-v]

Description

Currently, the khiops.sklearn module is tested by mocking the underlying khiops.core.api functions. Thus, for each method of the khiops.sklearn estimators one can define a series of mocked khiops.core.api functions.

However, the current testing framework does not support defining several mocks of the same khiops.core.api function for a khiops.sklearn estimator method. This is needed to be able to mock khiops.core.api functions that are called several times in the same khiops.sklearn estimator method call.

Questions/Ideas

• We need to add support for indexing function mocks with respect to their calling order inside the khiops.sklearn estimator method.
• This risks being brittle, because calling order (or even whether the same khiops.core.api function is called once or several times, for that matter!) can depend on the inputs.