message: update __init__.py for client
diff: # limitations under the License.
  # pylint: disable=doc-string-missing
  -from . import convert
  -from . import client
  from . import version
  -from . import io
  -from . import utils
  -from . import metric
  -
  -from convert import *
  -from client import *
  -from version import *
  -from io import *
  -from utils import *
  -from metric import *
  -
  -__all__ = convert.__all__ \
  - + client.__all__ \
  - + version.__all__ \
  - + io.__all__ \
  - + utils.__all__ \
  - + metric.__all__
  __version__ = version.serving_client_version
  