TestCommand.java

  public static void register(CommandDispatcher<ServerCommandSource> dispatcher,
                                CommandRegistryAccess ignoredCommandRegistryAccess,
                                CommandManager.RegistrationEnvironment ignoredRegistrationEnvironment)
    {
        dispatcher.register(LiteralArgumentBuilder
                .<ServerCommandSource>literal("ls")
                .then(CommandManager.argument("anyArgumentName", IntegerArgumentType.integer(-90, 90))
                        .executes(LsCommand::MethodToExecute)));
    }

    public static int MethodToExecute(CommandContext<ServerCommandSource> context) {
        Objects.requireNonNull(MinecraftClient.getInstance().player)
                .setPitch(IntegerArgumentType.getInteger(context, "anyArgumentName"));

        return 1;
    }