groupas list, optional
extraas nullable function, optional
lastKeyas nullable any) as function
binaryFormatparameter specifies the binary format of the key value.
groupparameter provides information about the group of known items.
extraparameter can be used to specify a function that will return a binary format value for the value following any key that was unexpected. If the
extraparameter is not specified, then an error will be raised if there are unexpected key values.
groupparameter specifies a list of item definitions. Each item definition is a list, containing 3-5 values, as follows:
BinaryOccurrence.Typevalue for how many times the item is expected to appear in the group. Required items that are not present cause an error. Required or optional duplicate items are handled like unexpected key values.