3.9 The instance type

delete($$s$)$
The delete($$s$) method deletes any element with string key $s$ from the instance. $

hasKey($$x$)$
The hasKey($$x$) method returns a boolean indicating whether the key $x$ exists in the instance. $

items()
The items() method returns a list of the [key,value] pairs in a instance.

keys()
The keys() method returns a list of the keys defined in a instance.

len()
The len() method returns the number of entries in a instance.

values()
The values() method returns a list of the values in a instance.