Using suffix and or environment variable no longer works
Setting a default for the mode (VCI) disables querying for the mode based on the suffix or the environment. Do we want this?
Argument{
.type = Argument::kString,
.nargs = 1,
.optshort = "m",
.optlong = "mode",
.defaultval = "mpi",
.required = false,
.help = "transport Layer to be used [REQUIRED]",
.p = &cmdline_args.virtual_cluster_implementation
},