Currently this method is fully supported only with Tensorflow 2.x and with
modules created by calling `export_savedmodel`. The method works in
both eager and graph modes.
Depending on the type of handle used, the call may involve downloading a
TensorFlow Hub module to a local cache location specified by the
`TFHUB_CACHE_DIR` environment variable. If a copy of the module is already
present in the TFHUB_CACHE_DIR, the download step is skipped.
Currently, three types of module handles are supported: 1) Smart URL resolvers
such as tfhub.dev, e.g.: https://tfhub.dev/google/nnlm-en-dim128/1. 2) A directory
on a file system supported by Tensorflow containing module files. This may include
a local directory (e.g. /usr/local/mymodule) or a Google Cloud Storage bucket
(gs://mymodule). 3) A URL pointing to a TGZ archive of a module, e.g.
https://example.com/mymodule.tar.gz.