How to access inventory_hostname from a filter_plugin?

My custom filter plugin uses ansible.utils.display to inject a warning in Ansible's output in some circumstances:

    if 'hold' in mydetails:
        display.warning('%s can be upgraded from %s to %s, but is on hold' %
                        (myp, mydetails['version'], latest))
        continue

This works and the warning is displayed nicely, but lacks the hostname -- which could get rather confusing, when one's inventory is large. I could insert the hostname there myself, but I want to use exactly the string already known as inventory_hostname. How would I access that variable?