code: public int getPositionStart(ModificationFeature mf)
  	{
  		Set vals = SITE_ACC.getValueFromBean(mf);
  
  		if (!vals.isEmpty())
  		{
  			return ((Integer) vals.iterator().next());
  		}
  
  		vals = INTERVAL_BEGIN_ACC.getValueFromBean(mf);
  
  		if (!vals.isEmpty())
  		{
  			return ((Integer) vals.iterator().next());
  		}
  
  		return -1;
  	}
docs: Gets the first position of the modification feature.
  @param mf modification feature
  @return first location