The key can be either specified in various ways see the Details section.
check_key(key = NULL)[character(1)]
a character string containing the API key or NULL
(see Details section on how to specify it)
if found the character string of the key, NULL otherwise
There are several ways to provide your API key.
The best way to know about them is to refer to the vignette about
"Setting Up Your API key" accessible with the following command:
vignette("setting_up_api_key", package = "rromeo").
You can also use rr_auth that will use the provided key to store it as
an environmental variable.