@CanIgnoreReturnValue
    public DuoSecurityUserAccount addGroup(final DuoSecurityUserAccountGroup group) {
        this.groups.add(group);
        return this;
    }
Add groups.

@param group the group
@return the duo security user account
support/cas-server-support-duo-core-mfa/src/main/java/org/apereo/cas/adaptors/duo/DuoSecurityUserAccount.java