public final int getRelativeOffset() {
    if (offset < 0) {
      throw new RuntimeException("offset not yet known");
    }

    return offset;
  }
Gets the relative item offset. The offset is from the start of the section which the instance
was written to.

@return {@code >= 0;} the offset
@throws RuntimeException thrown if the offset is not yet known
android/android_framework/dex-maker/src/main/java/com/android/dx/dex/file/OffsettedItem.java