code: public List<ManagementGroupVertex> getPredecessors() {
  
  		final List<ManagementGroupVertex> predecessors = new ArrayList<ManagementGroupVertex>();
  
  		for (ManagementGroupEdge edge : this.backwardEdges) {
  			predecessors.add(edge.getSource());
  		}
  
  		return predecessors;
  	}
docs: Returns the list of predecessors of this group vertex. A predecessors is a group vertex which can be reached via
  a group edge arriving at this group vertex.
  
  @return the list of predecessors of this group vertex.