Add comment on pre-processing to API docs
Add comment on pre-processing to API docs

bgyori/indra,johnbachman/indra,pvtodorov/indra,sorgerlab/belpy,pvtodorov/indra,bgyori/indra,bgyori/indra,pvtodorov/indra,johnbachman/indra,johnbachman/belpy,sorgerlab/belpy,sorgerlab/belpy,johnbachman/belpy,johnbachman/belpy,sorgerlab/indra,pvtodorov/indra,sorgerlab/indra,johnbachman/indra,sorgerlab/indra