@Override
 public boolean contains(Object arg0) {
   // TODO Auto-generated method stub
   if (!(arg0 instanceof TissueLikeMembrane)) return false;
   TissueLikeMembrane tlm = (TissueLikeMembrane) arg0;
   if (!cells.containsKey(tlm.getLabel())) return false;
   return cells.get(tlm.getLabel()).contains(arg0);
 }
  private boolean secureAdd(TissueLikeMembrane arg0) {
    String label = arg0.getLabel();
    List<TissueLikeMembrane> l;
    if (!cells.containsKey(label)) {
      l = new ArrayList<TissueLikeMembrane>();
      cells.put(label, l);
    } else l = cells.get(label);

    l.add(arg0);
    cellsById.put(arg0.getId(), arg0);

    return true;
  }
  protected boolean add(TissueLikeMembrane arg0) {
    // TODO Auto-generated method stub

    if (arg0.getLabel().equals(getEnvironmentLabel()))
      throw new IllegalArgumentException("Environment label");
    return secureAdd(arg0);
  }