externref property
Field for when this val is a WebAssembly externref value.
If this is set to 0 then it's a null externref, otherwise this must be
passed to wasmtime_externref_from_raw to determine the
wasmtime_externref_t.
Note that this field is always stored in a little-endian format.
Implementation
@ffi.Uint32()
external int externref;