get_key stops execution and returns an error message if the environment variable CN_API is not set to the user's API key. If the environment
variable is not set, the function returns an error message.
Usage
get_key()
Arguments
Value
The user's API key, if set as an environment variable. If key is not set, returns an error message indicating that the user can either set
the environment variable CN_API or pass the API key as an argument to the function.