Projection list does not support class attributes

[chmoder]

Environment details

1. Python 3.7.3
2. google-cloud-ndb 0.1.0

Steps to reproduce

1. ? Query with a projection list of ndbModel class attributes like this https://cloud.google.com/appengine/docs/standard/python/ndb/projectionqueries

Code example

class FooModel(ndb.Model):
    foo_attr = ndb.StringProperty()

FooModel.query(projection=[FooModel.foo_attr]).fetch()

Stack trace

ERROR:root:StringProperty('company', kind='Company') has type StringProperty, but expected one of: bytes, unicode
Traceback (most recent call last):
  File "/Users/tcross/development/virtual-environments/csgapi37/lib/python3.7/site-packages/webapp2.py", line 604, in dispatch
    return method(*args, **kwargs)
  File "/Users/tcross/development/csgapi37/med_supp.py", line 684, in get
    return self.get_our_companies(keys_only)
  File "/Users/tcross/development/csgapi37/med_supp.py", line 654, in get_our_companies
    our_companies = pool.map(callback, query)
  File "/usr/local/Cellar/python/3.7.3/Frameworks/Python.framework/Versions/3.7/lib/python3.7/multiprocessing/pool.py", line 268, in map
    return self._map_async(func, iterable, mapstar, chunksize).get()
  File "/usr/local/Cellar/python/3.7.3/Frameworks/Python.framework/Versions/3.7/lib/python3.7/multiprocessing/pool.py", line 383, in _map_async
    iterable = list(iterable)
  File "/Users/tcross/development/virtual-environments/csgapi37/lib/python3.7/site-packages/google/cloud/ndb/_datastore_query.py", line 596, in next
    if not self.has_next():
  File "/Users/tcross/development/virtual-environments/csgapi37/lib/python3.7/site-packages/google/cloud/ndb/_datastore_query.py", line 516, in has_next
    return self.has_next_async().result()
  File "/Users/tcross/development/virtual-environments/csgapi37/lib/python3.7/site-packages/google/cloud/ndb/tasklets.py", line 191, in result
    self.check_success()
  File "/Users/tcross/development/virtual-environments/csgapi37/lib/python3.7/site-packages/google/cloud/ndb/tasklets.py", line 138, in check_success
    raise self._exception
  File "/Users/tcross/development/virtual-environments/csgapi37/lib/python3.7/site-packages/google/cloud/ndb/tasklets.py", line 297, in _advance_tasklet
    type(error), error, error.__traceback__
  File "/Users/tcross/development/virtual-environments/csgapi37/lib/python3.7/site-packages/google/cloud/ndb/_datastore_query.py", line 534, in has_next_async
    result_set.has_next_async() for result_set in self._result_sets
  File "/Users/tcross/development/virtual-environments/csgapi37/lib/python3.7/site-packages/google/cloud/ndb/tasklets.py", line 297, in _advance_tasklet
    type(error), error, error.__traceback__
  File "/Users/tcross/development/virtual-environments/csgapi37/lib/python3.7/site-packages/google/cloud/ndb/_datastore_query.py", line 263, in has_next_async
    yield self._next_batch()  # First time
  File "/Users/tcross/development/virtual-environments/csgapi37/lib/python3.7/site-packages/google/cloud/ndb/tasklets.py", line 297, in _advance_tasklet
    type(error), error, error.__traceback__
  File "/Users/tcross/development/virtual-environments/csgapi37/lib/python3.7/site-packages/google/cloud/ndb/_datastore_query.py", line 291, in _next_batch
    response = yield _datastore_run_query(query)
  File "/Users/tcross/development/virtual-environments/csgapi37/lib/python3.7/site-packages/google/cloud/ndb/tasklets.py", line 301, in _advance_tasklet
    yielded = self.generator.send(send_value)
  File "/Users/tcross/development/virtual-environments/csgapi37/lib/python3.7/site-packages/google/cloud/ndb/_datastore_query.py", line 830, in _datastore_run_query
    query_pb = _query_to_protobuf(query)
  File "/Users/tcross/development/virtual-environments/csgapi37/lib/python3.7/site-packages/google/cloud/ndb/_datastore_query.py", line 737, in _query_to_protobuf
    for name in query.projection
  File "/Users/tcross/development/virtual-environments/csgapi37/lib/python3.7/site-packages/google/cloud/ndb/_datastore_query.py", line 737, in <listcomp>
    for name in query.projection
TypeError: StringProperty('company', kind='Company') has type StringProperty, but expected one of: bytes, unicode