dataset__call__() returns a FieldsSubsetDataSet, so still a subset of fields, but not cached any more. I added the function dataset.cached_fields_subset(self,*fieldnames) that returns the old version, cached, in case someone needs it. Current behaviour passes the tests.

import filetensor
import nnet_ops
import version

from lookup_list import LookupList

def __src_version__():
    #todo - this is vulnerable to the bug in theano ticket #160
    return version.src_version(__name__)