docs(firestore): standardize use of 'required' and 'optional' in docstrings; add py2 deprecation warning; add 3.8 unit tests (via synth)

[yoshi-automation]

This PR was generated using Autosynth. 🌈

Log from Synthtool

synthtool > Executing /tmpfs/src/git/autosynth/working_repo/firestore/synth.py.
synthtool > Ensuring dependencies.
synthtool > Pulling artman image.
latest: Pulling from googleapis/artman
Digest: sha256:264654a37596a44b0668b8ce6ac41082d713f6ee150b3fc6425fa78cc64e4f20
Status: Image is up to date for googleapis/artman:latest
synthtool > Cloning googleapis.
synthtool > Running generator for google/firestore/artman_firestore.yaml.
synthtool > Generated code into /home/kbuilder/.cache/synthtool/googleapis/artman-genfiles/python/firestore-v1beta1.
synthtool > Copy: /home/kbuilder/.cache/synthtool/googleapis/google/firestore/v1beta1/write.proto to /home/kbuilder/.cache/synthtool/googleapis/artman-genfiles/python/firestore-v1beta1/google/cloud/firestore_v1beta1/proto/write.proto
synthtool > Copy: /home/kbuilder/.cache/synthtool/googleapis/google/firestore/v1beta1/common.proto to /home/kbuilder/.cache/synthtool/googleapis/artman-genfiles/python/firestore-v1beta1/google/cloud/firestore_v1beta1/proto/common.proto
synthtool > Copy: /home/kbuilder/.cache/synthtool/googleapis/google/firestore/v1beta1/firestore.proto to /home/kbuilder/.cache/synthtool/googleapis/artman-genfiles/python/firestore-v1beta1/google/cloud/firestore_v1beta1/proto/firestore.proto
synthtool > Copy: /home/kbuilder/.cache/synthtool/googleapis/google/firestore/v1beta1/document.proto to /home/kbuilder/.cache/synthtool/googleapis/artman-genfiles/python/firestore-v1beta1/google/cloud/firestore_v1beta1/proto/document.proto
synthtool > Copy: /home/kbuilder/.cache/synthtool/googleapis/google/firestore/v1beta1/query.proto to /home/kbuilder/.cache/synthtool/googleapis/artman-genfiles/python/firestore-v1beta1/google/cloud/firestore_v1beta1/proto/query.proto
synthtool > Placed proto files into /home/kbuilder/.cache/synthtool/googleapis/artman-genfiles/python/firestore-v1beta1/google/cloud/firestore_v1beta1/proto.
synthtool > Replaced 'from google.cloud import firestore_v1beta1' in tests/unit/gapic/v1beta1/test_firestore_client_v1beta1.py.
synthtool > Replaced 'client = firestore_v1beta1.FirestoreClient' in tests/unit/gapic/v1beta1/test_firestore_client_v1beta1.py.
synthtool > Running generator for google/firestore/artman_firestore_v1.yaml.
synthtool > Generated code into /home/kbuilder/.cache/synthtool/googleapis/artman-genfiles/python/firestore-v1.
synthtool > Copy: /home/kbuilder/.cache/synthtool/googleapis/google/firestore/v1/write.proto to /home/kbuilder/.cache/synthtool/googleapis/artman-genfiles/python/firestore-v1/google/cloud/firestore_v1/proto/write.proto
synthtool > Copy: /home/kbuilder/.cache/synthtool/googleapis/google/firestore/v1/common.proto to /home/kbuilder/.cache/synthtool/googleapis/artman-genfiles/python/firestore-v1/google/cloud/firestore_v1/proto/common.proto
synthtool > Copy: /home/kbuilder/.cache/synthtool/googleapis/google/firestore/v1/firestore.proto to /home/kbuilder/.cache/synthtool/googleapis/artman-genfiles/python/firestore-v1/google/cloud/firestore_v1/proto/firestore.proto
synthtool > Copy: /home/kbuilder/.cache/synthtool/googleapis/google/firestore/v1/document.proto to /home/kbuilder/.cache/synthtool/googleapis/artman-genfiles/python/firestore-v1/google/cloud/firestore_v1/proto/document.proto
synthtool > Copy: /home/kbuilder/.cache/synthtool/googleapis/google/firestore/v1/query.proto to /home/kbuilder/.cache/synthtool/googleapis/artman-genfiles/python/firestore-v1/google/cloud/firestore_v1/proto/query.proto
synthtool > Placed proto files into /home/kbuilder/.cache/synthtool/googleapis/artman-genfiles/python/firestore-v1/google/cloud/firestore_v1/proto.
synthtool > Replaced 'from google.cloud import firestore_v1' in tests/unit/gapic/v1/test_firestore_client_v1.py.
synthtool > Replaced 'client = firestore_v1.FirestoreClient' in tests/unit/gapic/v1/test_firestore_client_v1.py.
synthtool > Running generator for google/firestore/admin/artman_firestore_v1.yaml.
synthtool > Generated code into /home/kbuilder/.cache/synthtool/googleapis/artman-genfiles/python/firestore-admin-v1.
synthtool > Copy: /home/kbuilder/.cache/synthtool/googleapis/google/firestore/admin/v1/index.proto to /home/kbuilder/.cache/synthtool/googleapis/artman-genfiles/python/firestore-admin-v1/google/cloud/firestore_admin_v1/proto/index.proto
synthtool > Copy: /home/kbuilder/.cache/synthtool/googleapis/google/firestore/admin/v1/firestore_admin.proto to /home/kbuilder/.cache/synthtool/googleapis/artman-genfiles/python/firestore-admin-v1/google/cloud/firestore_admin_v1/proto/firestore_admin.proto
synthtool > Copy: /home/kbuilder/.cache/synthtool/googleapis/google/firestore/admin/v1/location.proto to /home/kbuilder/.cache/synthtool/googleapis/artman-genfiles/python/firestore-admin-v1/google/cloud/firestore_admin_v1/proto/location.proto
synthtool > Copy: /home/kbuilder/.cache/synthtool/googleapis/google/firestore/admin/v1/field.proto to /home/kbuilder/.cache/synthtool/googleapis/artman-genfiles/python/firestore-admin-v1/google/cloud/firestore_admin_v1/proto/field.proto
synthtool > Copy: /home/kbuilder/.cache/synthtool/googleapis/google/firestore/admin/v1/operation.proto to /home/kbuilder/.cache/synthtool/googleapis/artman-genfiles/python/firestore-admin-v1/google/cloud/firestore_admin_v1/proto/operation.proto
synthtool > Placed proto files into /home/kbuilder/.cache/synthtool/googleapis/artman-genfiles/python/firestore-admin-v1/google/cloud/firestore_admin_v1/proto.
synthtool > Replaced "'google-cloud-firestore-admin'" in google/cloud/firestore_admin_v1/gapic/firestore_admin_client.py.
synthtool > Replaced 'from google\\.cloud\\.firestore\\.admin_v1.proto' in google/cloud/firestore_admin_v1/proto/field_pb2.py.
synthtool > Replaced 'from google\\.cloud\\.firestore\\.admin_v1.proto' in google/cloud/firestore_admin_v1/proto/firestore_admin_pb2_grpc.py.
synthtool > Replaced 'from google\\.cloud\\.firestore\\.admin_v1.proto' in google/cloud/firestore_admin_v1/proto/operation_pb2.py.
synthtool > Replaced 'from google\\.cloud\\.firestore\\.admin_v1.proto' in google/cloud/firestore_admin_v1/proto/firestore_admin_pb2.py.
.coveragerc
.flake8
MANIFEST.in
docs/_static/custom.css
docs/_templates/layout.html
noxfile.py.j2
setup.cfg
synthtool > Replaced 'GOOGLE_APPLICATION_CREDENTIALS' in noxfile.py.
synthtool > Replaced '"--quiet", system_test' in noxfile.py.
Running session blacken
Creating virtual environment (virtualenv) using python3.6 in .nox/blacken
pip install black==19.3b0
black docs google tests noxfile.py setup.py
reformatted /tmpfs/src/git/autosynth/working_repo/firestore/google/cloud/firestore_admin_v1/__init__.py
reformatted /tmpfs/src/git/autosynth/working_repo/firestore/google/cloud/firestore_admin_v1/gapic/enums.py
reformatted /tmpfs/src/git/autosynth/working_repo/firestore/google/cloud/firestore_admin_v1/gapic/firestore_admin_client_config.py
reformatted /tmpfs/src/git/autosynth/working_repo/firestore/google/cloud/firestore_admin_v1/proto/field_pb2_grpc.py
reformatted /tmpfs/src/git/autosynth/working_repo/firestore/google/cloud/firestore_admin_v1/gapic/transports/firestore_admin_grpc_transport.py
reformatted /tmpfs/src/git/autosynth/working_repo/firestore/google/cloud/firestore_admin_v1/proto/field_pb2.py
reformatted /tmpfs/src/git/autosynth/working_repo/firestore/google/cloud/firestore_admin_v1/proto/firestore_admin_pb2_grpc.py
reformatted /tmpfs/src/git/autosynth/working_repo/firestore/google/cloud/firestore_admin_v1/proto/index_pb2_grpc.py
reformatted /tmpfs/src/git/autosynth/working_repo/firestore/google/cloud/firestore_admin_v1/proto/location_pb2.py
reformatted /tmpfs/src/git/autosynth/working_repo/firestore/google/cloud/firestore_admin_v1/proto/location_pb2_grpc.py
reformatted /tmpfs/src/git/autosynth/working_repo/firestore/google/cloud/firestore_admin_v1/gapic/firestore_admin_client.py
reformatted /tmpfs/src/git/autosynth/working_repo/firestore/google/cloud/firestore_admin_v1/proto/operation_pb2_grpc.py
reformatted /tmpfs/src/git/autosynth/working_repo/firestore/google/cloud/firestore_admin_v1/types.py
reformatted /tmpfs/src/git/autosynth/working_repo/firestore/google/cloud/firestore_admin_v1/proto/index_pb2.py
reformatted /tmpfs/src/git/autosynth/working_repo/firestore/google/cloud/firestore_v1/gapic/enums.py
reformatted /tmpfs/src/git/autosynth/working_repo/firestore/google/cloud/firestore_v1/gapic/firestore_client_config.py
reformatted /tmpfs/src/git/autosynth/working_repo/firestore/google/cloud/firestore_admin_v1/proto/firestore_admin_pb2.py
reformatted /tmpfs/src/git/autosynth/working_repo/firestore/google/cloud/firestore_v1/gapic/transports/firestore_grpc_transport.py
reformatted /tmpfs/src/git/autosynth/working_repo/firestore/google/cloud/firestore_v1/proto/common_pb2_grpc.py
reformatted /tmpfs/src/git/autosynth/working_repo/firestore/google/cloud/firestore_admin_v1/proto/operation_pb2.py
reformatted /tmpfs/src/git/autosynth/working_repo/firestore/google/cloud/firestore_v1/proto/document_pb2_grpc.py
reformatted /tmpfs/src/git/autosynth/working_repo/firestore/google/cloud/firestore_v1/proto/common_pb2.py
reformatted /tmpfs/src/git/autosynth/working_repo/firestore/google/cloud/firestore_v1/gapic/firestore_client.py
reformatted /tmpfs/src/git/autosynth/working_repo/firestore/google/cloud/firestore_v1/proto/firestore_pb2_grpc.py
reformatted /tmpfs/src/git/autosynth/working_repo/firestore/google/cloud/firestore_v1/proto/query_pb2_grpc.py
reformatted /tmpfs/src/git/autosynth/working_repo/firestore/google/cloud/firestore_v1/proto/document_pb2.py
reformatted /tmpfs/src/git/autosynth/working_repo/firestore/google/cloud/firestore_v1/proto/query_pb2.py
reformatted /tmpfs/src/git/autosynth/working_repo/firestore/google/cloud/firestore_v1/proto/write_pb2_grpc.py
reformatted /tmpfs/src/git/autosynth/working_repo/firestore/google/cloud/firestore_v1beta1/gapic/enums.py
reformatted /tmpfs/src/git/autosynth/working_repo/firestore/google/cloud/firestore_v1/proto/write_pb2.py
reformatted /tmpfs/src/git/autosynth/working_repo/firestore/google/cloud/firestore_v1beta1/gapic/firestore_client_config.py
reformatted /tmpfs/src/git/autosynth/working_repo/firestore/google/cloud/firestore_v1beta1/gapic/transports/firestore_grpc_transport.py
reformatted /tmpfs/src/git/autosynth/working_repo/firestore/google/cloud/firestore_v1beta1/proto/common_pb2_grpc.py
reformatted /tmpfs/src/git/autosynth/working_repo/firestore/google/cloud/firestore_v1beta1/gapic/firestore_client.py
reformatted /tmpfs/src/git/autosynth/working_repo/firestore/google/cloud/firestore_v1beta1/proto/document_pb2_grpc.py
reformatted /tmpfs/src/git/autosynth/working_repo/firestore/google/cloud/firestore_v1beta1/proto/common_pb2.py
reformatted /tmpfs/src/git/autosynth/working_repo/firestore/google/cloud/firestore_v1beta1/proto/firestore_pb2_grpc.py
reformatted /tmpfs/src/git/autosynth/working_repo/firestore/google/cloud/firestore_v1/proto/firestore_pb2.py
reformatted /tmpfs/src/git/autosynth/working_repo/firestore/google/cloud/firestore_v1beta1/proto/query_pb2_grpc.py
reformatted /tmpfs/src/git/autosynth/working_repo/firestore/google/cloud/firestore_v1beta1/proto/document_pb2.py
reformatted /tmpfs/src/git/autosynth/working_repo/firestore/google/cloud/firestore_v1beta1/proto/query_pb2.py
reformatted /tmpfs/src/git/autosynth/working_repo/firestore/google/cloud/firestore_v1beta1/proto/write_pb2_grpc.py
reformatted /tmpfs/src/git/autosynth/working_repo/firestore/google/cloud/firestore_v1beta1/proto/write_pb2.py
reformatted /tmpfs/src/git/autosynth/working_repo/firestore/noxfile.py
reformatted /tmpfs/src/git/autosynth/working_repo/firestore/tests/unit/gapic/v1/test_firestore_admin_client_v1.py
reformatted /tmpfs/src/git/autosynth/working_repo/firestore/tests/unit/gapic/v1/test_firestore_client_v1.py
reformatted /tmpfs/src/git/autosynth/working_repo/firestore/tests/unit/gapic/v1beta1/test_firestore_client_v1beta1.py
reformatted /tmpfs/src/git/autosynth/working_repo/firestore/google/cloud/firestore_v1beta1/proto/firestore_pb2.py
All done! ✨ 🍰 ✨
48 files reformatted, 81 files left unchanged.
Session blacken was successful.
synthtool > Wrote metadata to synth.metadata.