code: public SectionHeader getSectionHeader(int number) {
          for (SectionHeader header : headers) {
              if (header.getNumber() == number) {
                  return header;
              }
          }
          throw new IllegalArgumentException(
                  "invalid section number, no section header found");
      }
docs: Returns the section entry that has the given number or null if there is
  no section with that number.
  
  @param number
  of the section
  @return the section table entry that has the given number
  @throw {@link IllegalArgumentException} if no section header for number
  found