doc_shared: NULL Object For Common Documentation
In uptasticsearch: Get Data Frame Representations of 'Elasticsearch' Results

This is a NULL object with documentation so that later functions can call inheritParams

`es_host`	A string identifying an Elasticsearch host. This should be of the form `[transfer_protocol][hostname]:[port]`. For example, `'http://myindex.thing.com:9200'`.
`es_index`	The name of an Elasticsearch index to be queried. Note that passing `NULL` is not supported. Technically, not passing an index to Elasticsearch is legal and results in searching over all indexes. To be sure that this very expensive query is not executed by accident, uptasticsearch forbids this. If you want to execute a query over all indexes in the cluster, set this argument to `"_all"`.