public void addIncomingEdge(final EdgeType edge){
  Preconditions.checkNotNull(edge,"Error: Edge argument can't be null");
  m_incomingEdges.add(edge);
}

public void addIncomingEdge ( final EdgeType edge ) { Preconditions . checkNotNull ( edge , "Error: Edge argument can't be null" ) ; m_incomingEdges . add ( edge ) ; }
adds an incoming edge to the node .
