static void generateEitherEnum(final Writer writer) throws IOException
    {
        indent(writer, 0, "#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]\n");
        indent(writer, 0, "pub enum Either<L, R> {\n");
        indent(writer, 1, "Left(L),\n");
        indent(writer, 1, "Right(R),\n");
        indent(writer, 0, "}\n\n");
    }
Create a new 'lib.rs' for the library being generated.

@param outputManager     for generating the codecs to.
@param byteOrder         for the Encoding.
@param schemaVersionType for acting_version type.
sbe-tool/src/main/java/uk/co/real_logic/sbe/generation/rust/LibRsDef.java