Thanks, but I followed the docs saying:
Alternatively, for CPU-support only, you can install  Transformers and PyTorch in one line with:
pip install transformers[torch]
I previously also did:
pip install transformers[tf-cpu]
What do I need to install / configure to make the CPU-only work for zero-shot learning?
FYI: The “pip list” output:
Package                Version

absl-py                0.11.0
apsw                   3.28.0.post1
apturl                 0.5.2
astunparse             1.6.3
beautifulsoup4         4.8.2
blinker                1.4
Brlapi                 0.7.0
cachetools             4.1.1
certifi                2019.11.28
chardet                3.0.4
chrome-gnome-shell     0.0.0
cliapp                 1.20180812.1
Click                  7.0
cmdtest                0.32+git
colorama               0.4.3
command-not-found      0.3
cryptography           2.8
css-parser             1.0.4
cssselect              1.1.0
cssutils               1.0.2
cupshelpers            1.0
dataclasses            0.6
dbus-python            1.2.16
defer                  1.0.6
distro                 1.4.0
distro-info            0.23ubuntu1
dnspython              1.16.0
entrypoints            0.3
feedparser             5.2.1
filelock               3.0.12
fire                   0.3.1
future                 0.18.2
gast                   0.3.3
google-auth            1.23.0
google-auth-oauthlib   0.4.2
google-pasta           0.2.0
grpcio                 1.34.0
h5py                   2.10.0
html2text              2020.1.16
html5-parser           0.4.9
html5lib               1.0.1
httplib2               0.14.0
httptools              0.1.1
idna                   2.8
ifaddr                 0.1.6
joblib                 0.17.0
Keras-Preprocessing    1.1.2
keras2onnx             1.7.0
keyring                18.0.1
language-selector      0.1
launchpadlib           1.10.13
lazr.restfulclient     0.14.2
lazr.uri               1.0.3
louis                  3.12.0
lxml                   4.5.0
macaroonbakery         1.3.1
Markdown               3.1.1
mechanize              0.4.5
msgpack                0.6.2
netifaces              0.10.4
nose                   1.3.7
numpy                  1.19.4
oauthlib               3.1.0
olefile                0.46
onnx                   1.8.0
onnxconverter-common   1.7.0
opt-einsum             3.3.0
packaging              20.3
pexpect                4.6.0
Pillow                 7.0.0
pip                    20.0.2
protobuf               3.6.1
pyasn1                 0.4.8
pyasn1-modules         0.2.8
pycairo                1.16.2
pychm                  0.8.6
pycups                 1.9.73
Pygments               2.3.1
PyGObject              3.36.0
PyJWT                  1.7.1
pymacaroons            0.13.0
PyNaCl                 1.3.0
pyparsing              2.4.6
PyQt5                  5.14.1
PyQtWebEngine          5.14.0
pyRFC3339              1.1
python-apt             2.0.0+ubuntu0.20.4.2
python-dateutil        2.7.3
python-debian          0.1.36ubuntu1
pytz                   2019.3
pyxdg                  0.26
PyYAML                 5.3.1
regex                  2019.8.19
reportlab              3.5.34
repoze.lru             0.7
requests               2.22.0
requests-oauthlib      1.3.0
requests-unixsocket    0.2.0
Routes                 2.4.1
rsa                    4.6
sacremoses             0.0.43
SecretStorage          2.3.1
sentencepiece          0.1.94
setuptools             45.2.0
simplejson             3.16.0
sip                    4.19.21
six                    1.14.0
soupsieve              1.9.5
systemd-python         234
tensorboard            2.4.0
tensorboard-plugin-wit 1.7.0
tensorflow-cpu         2.3.1
tensorflow-estimator   2.3.0
termcolor              1.1.0
tokenizers             0.9.4
torch                  1.7.0
tqdm                   4.54.1
transformers           4.0.1
ttystatus              0.38
typing-extensions      3.7.4.3
ubuntu-advantage-tools 20.3
ubuntu-drivers-common  0.0.0
ufw                    0.36
unattended-upgrades    0.1
urllib3                1.25.8
wadllib                1.3.3
webencodings           0.5.1
WebOb                  1.8.5
Werkzeug               1.0.1
wheel                  0.34.2
wrapt                  1.12.1
xkit                   0.0.0
zeroconf               0.24.4