@Override
    public String getMessage() {
        if (this.requiredSenderTypes.size() == 1) {
            return String.format(
                    "%s is not allowed to execute that command. Must be of type %s",
                    commandSender().getClass().getSimpleName(),
                    TypeUtils.simpleName(this.requiredSenderTypes.iterator().next())
            );
        }
        return String.format(
                "%s is not allowed to execute that command. Must be one of %s",
                commandSender().getClass().getSimpleName(),
                this.requiredSenderTypes.stream().map(TypeUtils::simpleName).collect(Collectors.joining(", "))
        );
    }
Returns the required sender types, a sender must satisfy one.

@return required sender types
cloud-core/src/main/java/org/incendo/cloud/exception/InvalidCommandSenderException.java