code: private void expand(String mediaQueryPath, Section section, List<Section> stack) {
          stack = new ArrayList<>(stack);
          if (!section.getSelectors().isEmpty()) {
              expandSection(mediaQueryPath, section, stack);
          } else {
              mediaQueryPath = expandMediaQuery(mediaQueryPath, section, stack);
          }
  
          if (section.getSelectorString() != null && !section.getSelectorString().startsWith("@")) {
              // Unfold subsections
              for (Section child : section.getSubSections()) {
                  expand(mediaQueryPath, child, stack);
              }
  
              // Delete subsections - no longer necessary (and not supported by css)
              section.getSubSections().clear();
          }
      }
docs: /*
  Expands nested sections / media queries into a flat structure as expected by CSS