Open
Description
It will be more easier to check metadata using JSON instead of Python's pickle.
For the preprocess function kept in metadata, we could save directly the source code of the function used in string. The metadata will be more portable. So end-users not using Python would be able to read the source code and understand the objective of the preprocessing that have been applied. For Python's users a simple call to the eval function should suffice to redefine the preprocessing function used.