<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def should_audit(instance):
 """Returns True or False to indicate whether the instance should be audited or not, depending on the project settings."""


    # do not audit any model listed in UNREGISTERED_CLASSES
    for unregistered_class in UNREGISTERED_CLASSES:
        if isinstance(instance, unregistered_class):
            return False

    # only audit models listed in REGISTERED_CLASSES (if it's set)
    if len(REGISTERED_CLASSES) > 0:
        for registered_class in REGISTERED_CLASSES:
            if isinstance(instance, registered_class):
                break
        else:
            return False

    # all good
    return True