mongoc_uri_get_option_as_utf8(3) on Linux
The text 654efcb3454d, as Debian 9 (Stretch) shipped it.
Returns the value of the URI option if it is set and of the correct type (string). This value is a pointer into the URI's internal buffer, and is only valid until the URI is modified or freed. If the option is not set, or set to an invalid type, returns fallback.