Get the namespace of the current event. This will only be called when the
current event type is StartElement. If the InfosetInputter does not
support namespaces, this shoud return null. This may return null to
represent no namespaces.
Get the content of a simple type. This will only be called when the
current event type is StartElement and the element is a simple type. If
the event contains complex data, it is an error and should throw
NonTextFoundInSimpleContentException. If the element does not have any
simple content, this should return either null or the empty string.
Determine if the current event is nilled. This will only be called when
the current event type is StartElement. Return MaybeBoolean.Nope if no
nil property is set, which implies the element is not nilled. Return
MaybeBoolean(false) if the nil property is set, but it is set to false.
Return MaybeBoolean(true) if the nil property is set to true.