The get_time_interval_string() is a good utility function for displaying time duration between timestamps. However, I think we can further improve on this by adding the following options:

1. Allow dropping zero units.
   • If the format is not supplied, the format defaults to "dateintervaldayshoursmins" with a format of "%ad %hh %im". Let's say that we have an interval of 3 days, the function will return "3d 0h 0s". It would look simpler if we can drop the zero-time units.
2. Allow the option to display full format for time units
   • If format is not supplied, provide the option to display the time units in full format. E.g. instead of returning "3d", we can return "3 days" instead.