code: public static String getPropertyValue( AbstractBlockHolder holder, String propertyName ) {
  		BlockProperty p = holder.findPropertyBlockByName( propertyName );
  		return p == null ? null : p.getValue();
  	}
docs: Gets the value of a property.
  @param holder a property holder (not null)
  @param propertyName a property name (not null)
  @return the property value, which can be null, or null if the property was not found