src/main/java/org/helm/notation2/parser/notation/polymer/PolymerNotation.java
private void setPolymerElements() {
    if (polymerID instanceof RNAEntity || polymerID instanceof PeptideEntity) {
      this.polymerElements = new PolymerListElements(polymerID);
    } else {
      this.polymerElements = new PolymerSingleElements(polymerID);
    }

  }
private void setPolymerElements() {
    if (polymerID instanceof RNAEntity || polymerID instanceof PeptideEntity) {
      this.polymerElements = new PolymerListElements(polymerID);
    } else {
      this.polymerElements = new PolymerSingleElements(polymerID);
    }

  }
method to generate the right PolymerElements, in the case of Chem and Blob
only one Monomer is allowed