code: public PublicationsHandler build() throws KSIException {
          Util.notNull(publicationsFileClient, "KSI publications file");
          Util.notNull(certSelector, "KSI publications file trusted certificate selector");
  
          if (trustStore == null) {
              this.setPublicationsFilePkiTrustStore(new File(getDefaultTrustStore()), null);
          }
          PKITrustStore jksTrustStore = new JKSTrustStore(trustStore, certSelector);
          PublicationsFileFactory publicationsFileFactory = new InMemoryPublicationsFileFactory(jksTrustStore);
          PublicationsFileClientAdapter publicationsFileAdapter = createPublicationsFileAdapter(publicationsFileClient, publicationsFileFactory, publicationsFileCacheExpirationTime);
  
          return new PublicationsHandlerImpl(publicationsFileAdapter);
      }
docs: Builds the {@link PublicationsHandler} instance.  Checks that publications file client and
  KSI publications file trusted certificate selector are set. If not configured, {@link NullPointerException} is thrown.
  
  @return Publications handler ({@link PublicationsHandler}).
  @throws KSIException
  will be thrown when errors occur on {@link PublicationsHandler} class initialization.