code: @NonNull
      public ReplicatorConfiguration setPullFilter(ReplicationFilter pullFilter) {
          if (readonly) { throw new IllegalStateException("ReplicatorConfiguration is readonly mode."); }
          this.pullFilter = pullFilter;
          return getReplicatorConfiguration();
      }
docs: Sets a filter object for validating whether the documents can be pulled from the
  remote endpoint. Only documents for which the object returns true are replicated.
  
  @param pullFilter The filter to filter the document to be pulled.
  @return The self object.