StandardType<T>'s which do not define a way to MPI_Type T should inherit from this class.
This class is primarily defined for backwards compatability because it defines is_fixed_type = false for non-fixed/non-mpi-typed StandardTypes. This class also provides a fairly convenient way to define communication overloads that are antithetical to DataType counterparts. E.g. when doing our parallel algorithms we may build a StandardType and then call communication routines with that type. We want to ensure that we dispatch to different methods when StandardType defines MPI typing vs. when it does not. The DataType vs. NotADataType typing accomplishes that goal
Definition at line 120 of file data_type.h.