code: public SortableBehavior setAxis(AxisEnum axis)
  	{
  		this.options.putLiteral("axis", axis != null ? axis.toString().toLowerCase() : null);
  		return this;
  	}
docs: If defined, the items can be dragged only horizontally or vertically. Possible
  values:'x', 'y'.
  
  @param axis
  @return instance of the current behavior