HELP METHOD Valid Only for User-Defined Methods
You can only submit a HELP METHOD request against a user-defined method. This is why you cannot specify MUTATOR or OBSERVER as method types, because mutator and observer methods are both system-generated.
If you attempt to perform the statement by specifying the name of a system-generated method, the request aborts and the system returns an error to the requestor.
SELF Parameter
The first parameter listed in a HELP METHOD report is the first parameter, named SELF, that the system generates internally by default.