code: @NonNull
      public ReplicatorConfiguration setPushFilter(ReplicationFilter pushFilter) {
          if (readonly) { throw new IllegalStateException("ReplicatorConfiguration is readonly mode."); }
          this.pushFilter = pushFilter;
          return getReplicatorConfiguration();
      }
docs: Sets a filter object for validating whether the documents can be pushed
  to the remote endpoint.
  
  @param pushFilter The filter to filter the document to be pushed.
  @return The self object.