public Section addSection(String sectionName) {
        String name = cleanName(sectionName);
        Section section = getSection(name);
        if (section == null) {
            section = new Section(name);
            this.sections.put(name, section);
        }
        return section;
    }
Ensures a section with the specified name exists, adding a new one if it does not yet exist.

@param sectionName the name of the section to ensure existence
@return the section created if it did not yet exist, or the existing Section that already existed.
config/core/src/main/java/org/apache/shiro/config/Ini.java