Remove truelearn.utils.persistent

[yuxqiu]

Currently, we keep the truelearn.utils.persistent in our package. However, it seems that they are redundant since we have already supported the method to convert AbstractKnowledgeComponent to dict. Given the dict, it's possible for users to use their library to convert the dictionary to other formats.

Thus, I propose that we could probably remove truelearn.utils.persistent.

[yuxqiu]

Could Have Reasons:

• probably could provide customization if we encapsulate the dump/load methods

If we have time:

• Implement JSON/pickle dump
• Implement JSON/pickle load

[KD-7]

Yea i agree with this, we can have a to_json and load_json functions etc

[KD-7]

After considering this option we decided to remove persistant, in future something similar to this could be added that made use of PMML. The justification being we generally wanted to follow the scikit-learn convention, and wrapping one line commands to pickle/json dump in this module wouldnt have followed this or been significantly useful.