code: public SectionHeader getSectionHeader(String sectionName) {
          for (SectionHeader entry : headers) {
              if (entry.getName().equals(sectionName)) {
                  return entry;
              }
          }
          throw new IllegalArgumentException(
                  "invalid section name, no section header found");
      }
docs: Returns the section entry that has the given name. If there are several
  sections with the same name, the first one will be returned.
  
  @param sectionName
  name of the section
  @return the section table entry that has the given sectionName
  @throw {@link IllegalArgumentException} if no section header for name
  found