code: private Expr translateAsUnknown(WyilFile.Expr expr, LocalEnvironment environment) {
  		// What we're doing here is creating a completely fresh variable to
  		// represent the return value. This is basically saying the return value
  		// could be anything, and we don't care what.
  		String name = "r" + Integer.toString(expr.getIndex());
  		WyalFile.Type type = convert(expr.getType(), expr);
  		WyalFile.VariableDeclaration vf = allocate(
  				new WyalFile.VariableDeclaration(type, new WyalFile.Identifier(name)), null);
  		// environment = environment.write(expr.getIndex());
  		// WyalFile.VariableDeclaration r = environment.read(expr.getIndex());
  		return new Expr.VariableAccess(vf);
  		// throw new IllegalArgumentException("Implement me");
  	}
docs: Translating as unknown basically means we're not representing the operation
  in question at the verification level. This could be something that we'll
  implement in the future, or maybe not.
  
  @param expr
  @param environment
  @return