Access tokens expire after four hours. Thus, this function should
be run each time you utilize the package and may need to be
re-called periodically if you have a session open for a long
duration.
It is not recommended that these authentication parameters be
stored directly in your code. There are various methods and
packages available that are more secure; this package does not
require you to use any one in particular.
More information on this available at https://developer.ibm.com/
customer-engagement/tutorials/
getting-started-oauth-watson-campaign-automation/ .