knowledge: PEP8 and PEP257 improvements
knowledge: PEP8 and PEP257 improvements

* Removes `__init__` methods.  (PR #2184)

Co-authored-by: Javier Martin Montull <ea6b80e26c65acc242d8916fb6eefa01b123cb69@cern.ch>
Signed-off-by: Jiri Kuncar <2bdffcb416fed3002465740d19a053a39918cbe5@cern.ch>

tiborsimko/invenio,tiborsimko/invenio,inveniosoftware/invenio,inveniosoftware/invenio