Support HTTP proxies in eland_import_hub_model

docs/guide/machine-learning.asciidoc

@@ -60,6 +60,12 @@ $ eland_import_hub_model <authentication> \ <1>
 <4> Specify the type of NLP task. Supported values are `fill_mask`, `ner`,
 `question_answering`, `text_classification`, `text_embedding`, and `zero_shot_classification`.
 
+For more information about the available options, run `eland_import_hub_model` with the `--help` option.
+
+[source,bash]
+------------------------
+$ eland_import_hub_model --help
+------------------------
 
 [discrete]
 [[ml-nlp-pytorch-docker]]
@@ -148,6 +154,23 @@ underscores `__`.
 
 --
 
+[discrete]
+[[ml-nlp-pytorch-proxy]]
+==== Connect to Elasticsearch through a proxy
+
+Behind the scenes, Eland uses the `requests` Python library, which
+https://requests.readthedocs.io/en/latest/user/advanced/#proxies[allows configuring
+proxies through an environment variable]. For example, to use an HTTP proxy to connect to
+an HTTPS Elasticsearch cluster, you need to set the `HTTPS_PROXY` environment variable
+when invoking Eland:
+
+[source,bash]
+--------------------------------------------------
+HTTPS_PROXY=http://proxy-host:proxy-port eland_import_hub_model ...
+--------------------------------------------------
+
+If you disabled security on your Elasticsearch cluster, you should use `HTTP_PROXY`
+instead.
 
 [discrete]
 [[ml-nlp-pytorch-auth]]
@@ -191,3 +214,28 @@ eland_import_hub_model --es-api-key <api-key> --url https://<hostname>:<port> ..
 eland_import_hub_model --hub-access-token <access-token> ...
 --------------------------------------------------
 --
+
+[discrete]
+[[ml-nlp-pytorch-tls]]
+==== TLS/SSL
+
+The following TLS/SSL options for Elasticsearch are available when using the import script:
+
+
+* Specify alternate CA bundle to verify the cluster certificate:
++
+--
+[source,bash]
+--------------------------------------------------
+eland_import_hub_model --ca-certs CA_CERTS ...
+--------------------------------------------------
+--
+
+* Disable TLS/SSL verification altogether (strongly discouraged):
++
+--
+[source,bash]
+--------------------------------------------------
+eland_import_hub_model --insecure ...
+--------------------------------------------------
+--

eland/cli/eland_import_hub_model.py

@@ -164,6 +164,7 @@ def get_es_client(cli_args, logger):
             "request_timeout": 300,
             "verify_certs": cli_args.insecure,
             "ca_certs": cli_args.ca_certs,
+            "node_class": "requests",
         }
 
         # Deployment location