code: @Override
      public IDocumentStore initialize() {
          if (initialized) {
              return this;
          }
  
          assertValidConfiguration();
  
          try {
              if (getConventions().getDocumentIdGenerator() == null) { // don't overwrite what the user is doing
                  MultiDatabaseHiLoIdGenerator generator = new MultiDatabaseHiLoIdGenerator(this, getConventions());
                  _multiDbHiLo = generator;
  
                  getConventions().setDocumentIdGenerator(generator::generateDocumentId);
              }
  
              getConventions().freeze();
              initialized = true;
          } catch (Exception e) {
              close();
              throw ExceptionsUtils.unwrapException(e);
          }
  
          return this;
      }
docs: Initializes this instance.