code: public PGPPublicKeyRingCollection getTrustedAnnouncedKeys()
              throws IOException, PGPException {
          PGPPublicKeyRingCollection announced = getAnnouncedPublicKeys();
          PGPPublicKeyRingCollection trusted = getPublicKeysOfTrustState(announced, OpenPgpTrustStore.Trust.trusted);
          return trusted;
      }
docs: Return a {@link PGPPublicKeyRingCollection} which contains all public keys of the contact, which are announced,
  as well as marked as {@link OpenPgpStore.Trust#trusted}.
  
  @return announced, trusted keys.
  
  @throws IOException IO error
  @throws PGPException PGP error