docs: @Exported(name="labelExpression")
      public String getAssignedLabelString() {
          if (canRoam || assignedNode==null)    return null;
          try {
              LabelExpression.parseExpression(assignedNode);
              return assignedNode;
          } catch (ANTLRException e) {
              // must be old label or host name that includes whitespace or other unsafe chars
              return LabelAtom.escape(assignedNode);
          }
      }