code: public void setBREE(String bree) {
  		String old = mainAttributes.get(BUNDLE_REQUIREDEXECUTIONENVIRONMENT);
  		if (!bree.equals(old)) {
  			this.mainAttributes.put(BUNDLE_REQUIREDEXECUTIONENVIRONMENT, bree);
  			this.modified = true;
  			this.bree = bree;
  		}
  	}
docs: Set the main attribute "Bundle-RequiredExecutionEnvironment" to the given
  value.
  
  @param bree The new value