from-import does not support "string"

[behrica]

This syntax cannot be used in libpython-clj,

from yellowbrick.contrib.wrapper import CLASSIFIER

when classifier is a String.

(py/from-import yellowbrick.contrib.wrapper CLASSIFIER)

fails with

 Unhandled java.lang.IllegalArgumentException
   No implementation of method: :get-attr of protocol:
   #'libpython-clj2.python.protocols/PPyAttr found for class: java.lang.String

          core_deftype.clj:  583  clojure.core/-cache-protocol-fn