code: void addGroupMember(final ManagementVertex vertex) {
  
  		while (this.groupMembers.size() <= vertex.getIndexInGroup()) {
  			this.groupMembers.add(null);
  		}
  
  		this.groupMembers.set(vertex.getIndexInGroup(), vertex);
  
  		this.getGraph().addVertex(vertex.getID(), vertex);
  	}
docs: Adds a {@link ManagementVertex} to this group vertex.
  
  @param vertex
  the vertex to be added