class Header(h.Struct): length = h.InclusiveLengthField(h.UInt16)
class B(h.Struct): a = h.UInt16 length_field = h.InclusiveLengthField(h.UInt16)
class T(h.Struct): x = h.InclusiveLengthField(h.UInt8) y = h.Array(10, fill=True)