code: public boolean hasRelatedSignatureId() {
          JSONObject metadata = (JSONObject) get(EVENT_METADATA);
          if (metadata == null) {
              return false;
          }
          return metadata.has(RELATED_SIGNATURE_ID) && !metadata.isNull(RELATED_SIGNATURE_ID);
      }
docs: Utility method to determine if this event has a related signature ID.
  
  @return true if this field exists and is set, false otherwise