API and documentation of preprocessors #842
Description
There are two preprocessors: task-level and estimator-level. The former is `automl._preprocess()` and the latter is `automl.model._preprocess()`. The former should be called before the latter. Right now they are not exposed as user-facing APIs.
We can add some user-facing APIs in future version. If you have any ideas for that please feel free to suggest.
Originally posted by @sonichi in #228 (reply in thread)