public HelpPrinter param(String longName, String shortName, String exampleValue, String description) {
        args.add(Arg.parameter(longName, shortName, exampleValue, description));
        return this;
    }
Adds a parameter that requires an argument value.

@param longName Nullable argument long form (e.g., "--foo").
@param shortName Nullable argument short form (e.g., null).
@param exampleValue Example value of the parameter (e.g., "FOO").
@param description Description description of the argument.
@return Returns the printer.
smithy-cli/src/main/java/software/amazon/smithy/cli/HelpPrinter.java